3 pm Jan 30, 2013

## CBSE Board mathematics examination

As part of the IBNLive-Topper chat series, Smita Kalra, mathematics teacher, will interact with students who will appear for the 2013 CBSE Board examinations which start from March 1. Parents and teachers can also benefit from her tips.

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52 questions answered | 4 questions pending

- how to do this ? A cylindrical tub of radius 16cm contains water to depth of 30cm . A spherical iron ball is dropped into the tub and the level of water is increased by 9cm . What is the radius of the ball ? Asked by:
**Saranvanan** - Smita Kalra The volume of the spherical ball would be exactly equal to the volume of the increased water column in the cylinder; V = Pi x r2 x h => Pi x 16^2 x (39 -30) = (Pi x 256 x 9) cu. cm. The volume of spherical ball = 4/3 x Pi x r^3, where r is the radius of the ball. Thus, Equating the two volumes, we get the radius of the ball.
- how to do this ? A cylindrical tub of radius 16cm contains water to depth of 30cm . A spherical iron ball is dropped into the tub and the level of water is increased by 9cm . What is the radius of the ball ? Asked by:
**Saran** - Smita Kalra The volume of the spherical ball would be exactly equal to the volume of the increased water column in the cylinder; V = Pi x r2 x h => Pi x 16^2 x (39 -30) = (Pi x 256 x 9) cu. cm. The volume of spherical ball = 4/3 x Pi x r^3, where r is the radius of the ball. Thus, Equating the two volumes, we get the radius of the ball.
- can you give the steps of construction for this construction... construct a tangent to a circle of radius 3 cm from a point on the concentric circle of radius 0.5 cm and measure its length. Asked by:
**manisha** - Smita Kalra There seems some mistake in the question you posted. Please cross check the radius of the concentric circle. Still the steps of construction in such type of questions are as follows: 1. Draw a circle of r cm (smaller one) radius with centre as O on the given plane. 2. Draw a circle of R cm radius taking O as its centre. Locate a point P on this circle and join OP. 3. Bisect OP. Let M be the midpoint of PO. 4. Taking M as its centre and MO as its radius draw a circle. Let it intersects the given circle at the points Q and R. 5. Join PQ and PR. PQ and PR are the required tangents
- The height of a cone is 60 cm .A small cone is cut off at the top by a plane parallel to the base and its volume is 1/64 the volume of the original cone . Find the height from the base at which the section is made Asked by:
**Anirudh** - Smita Kalra Let height of the original cone r 1 and h 1 be the radius and respectively. Let the radius and height of the cone that was cut off be r 2 and h 2 respectively. B and D are the centers of the bases of these cones Given, h 1 = AB = 60 cm In ∆ADE and ∆ABC ∠DAE = ∠BAC (Common) ∠ADE = ∠ABC (Corresponding angles as DE || BC) ∴ ∆ADE ∼ ∆ABC (AA similarity) So, AD/AB = DE/BC This gives, h2/h1 = r2/r1 It is given that volume of cone AXE / Volume of cone AYC = 1/64 Use the formula to get h2 = 15 cm Thus, the smaller cone is cut at a distance of 60 - 15 = 45 cm above the base.
- mam if we know the answers of other questions can we answer that? Asked by:
**vandna** - Smita Kalra Please explain. What you want to ask is not clear.
- i want to go to pace, so is it good? Asked by:
**Geny** - Smita Kalra Yes it is.
- May god bless u n may u succeed in ur life...........thank u for helping me in maths :-) Asked by:
**Geny** - Smita Kalra Thank you so much. All the very best for your exams. Hope you do very well in all your exams and pass with flying colours.
- What is real numbers, composite numbers, even numbers, odd numbers, prime number, whole numbers, natural numbers. Asked by:
**Ishant** - Smita Kalra Real numbers: Rational and irrational numbers together constitute Real numbers. Composite numbers: A number that has at least one positive divisor other than one or itself. Even numbers: Numbers which are divisible by 2. Odd numbers: Numbers which are not divisible by 2. Prime number: Number that has no positive divisor other than one or itself. The number 1 is neither composite nor prime. Whole numbers: 0 when included with the natural numbers Natural numbers: Numbers 1, 2, 3……., which are used for counting
- how many hour i study maths a day. Asked by:
**pragya** - Smita Kalra It depends on your preparation. First get your basics right. Then, to know how well you have prepared, you can attempt the sample papers available on the site www.topperlearning.com. Once you attempt those, you will get to know your weaker areas and then you can devote proper time to all the subjects.
- In the figure, chord PQ is parallel to the diameter RS of the circle. Given that angle SBP = 55o, the measure of angle QPS is Asked by:
**Geny** - Smita Kalra Please cross check the question you posted, specially the information about the given measure of angle.
- Half of a herd of deer are grazing in the field and three fourths of the remaining are playing nearby.The rest 9 are drinking water from the pond. Find the number of deer in the herd. (a) 75 (b) 76 (c) 71 (d) 72 and how, explain? Asked by:
**Geny** - Smita Kalra let the number of deer be x number of deer grazing in the field =x/2 Remaining deers = x - x/2 = x/2 number of deer playing nearby=3/4 x x/2 = 3x /8 number of deer drinking water from the pond = 9 x - ( x/2 + 3x / 8 ) =9 Solve this equation to get x = number of deers = 72
- Find sum 5+11+19+29+41+....? Asked by:
**vandna** - Smita Kalra This answer cannot be explained here properly. So, kindly post this query in 'ask the expert' section on the site www.topperlearning.com
- Two tangents make an angle of 120 to a radius of circle with 6 cm find the length of the two tangents Asked by:
**Anirudh** - Smita Kalra Let P be the external points and PA and PB be the two tangents drawn to the circle with centre O. We know that tangents drawn from an external point are equally inclined to the line joining that point to the centre So, angle APO = angle BPO = 30 degrees Now In ∆OAP ∠OAP = 90° In triangle OAP, tan 60 = OA/AP Put the values to get length of tangent = AP = 2 root 3 cm
- Two tangents making an angle of 120 with each other ,are drawn to a circle of radius 6 cm then the length of the two tangents are? Asked by:
**Anirudh** - Smita Kalra Let P be the external points and PA and PB be the two tangents drawn to the circle with centre O. We know that tangents drawn from an external point are equally inclined to the line joining that point to the centre So, angle APO = angle BPO = 30 degrees Now In ∆OAP ∠OAP = 90° In triangle OAP, tan 60 = OA/AP Put the values to get length of tangent = AP = 2 root 3 cm
- THe cost of painting the total outside surface of a closed cylindrical oil tank at 60 paise per sq.dm is Rs.237.60 . The height of tank is 6 times the radius of base of tank . Find the volume of the cylindrical tank correct to two decimal places . Asked by:
**Saravanan** - Smita Kalra Let r and h be the radius and height of the cylindrical tank. Given, h = 6r Total surface area of the closed cylindrical tank = 2 pi r(r + h) = 44 r^2 Cost of painting 1 dm^2 = Rs 0.6 Cost of painting 44r^2 dm^2 = Rs 0.6 × 44r^2 Total cost of painting the closed cylindrical tank = Rs 237.60 Therefore, 0.6 × 44r^2 = 237.60 Solve this to get r = 3 Thereafter find the height from the relation h = 6r Then you can find the Volume of the cylindrical tank by using the formula and putting in the values.
- Plz help me with this .... A hollow cube of side 4cm contains a solid sphere touching its sides. Find the volume of gaps between the sphere and the wall of the cube . Asked by:
**Saranvanan** - Smita Kalra side of cube=4cm so, when the sphere's side is touching the sides then the highest radius would be 2 cm volume of cube= a3 so 4*4*4*=64 volume of sphere having radium 2cm= 4/3*pie*r*r*r =33.52 volume of gaps between the sphere and wall would be volume of cube - volume of sphere =64-33.52 =30.48
- How to get full marks in maths? Asked by:
**Geny** - Smita Kalra Revise your concepts thoroughly, practice all the questions of ncert and go through the past year papers too. Also, you can practice the sample papers available on the site www.topperlearning.com
- is derivation of frustum related formula will come in 10th exams Asked by:
**ansh** - Smita Kalra Derivation of its formula is usually not asked. But you should know it, it is very easy too.
- Topper peboard benefits and also tell about that it contains any important questions or not. Asked by:
**Ishant** - Smita Kalra Topper peboard will definitely be of benefit to you.
- A hemispherical bowl of internal and external diameters 6 cm and 10 cm is melted and formed into a right circular cylinder of radius 14cm . Find the height of the cylinder . Asked by:
**Saranvanan** - Smita Kalra We have: Volume of hemispherical bowl = Volume of cylinder 2/3 x 22/7 x (R^2 - r^2) = 22/7 x r^2 x h Put in the values to get the height of the cylinder.
- Rain water which falls on a flat rectangular surface of length 6 m and breadth 4 m is transferred into a cylindrical vessel of internal radius 20 cm. What will be the height of water in the cylindrical vessel, if the rainfall is 1 cm Asked by:
**farooq** - Smita Kalra Length = 6m, breadth = 4m Rainfall (height of cuboid) = 2 cm = 0.2 m Volume of water = lbh = 0.48 m^3 let height of cylinder = h Radius of cylinder = 20 cm = 0.2 m VOlume of water in cyl = Volume of water in cuboid 22/7 x (0.2)(0.2) h = 0.48 Solve this equation to get the value of h.
- two pipes running together can fill a cistren in 40/13 minutes.if one pipe takes 3 minutes more than the other to fill it ,find the time in which each pipe would fill the cistern. Asked by:
**devanjan** - Smita Kalra Let First pipe takes x mins Second pipe takes = (x + 3) mins Let volume of cistern be V Volume - filled by first pipe in 1 min = V/x Volume - filled by second pipe in 1 min = V/x+3 VOlume - filled by both pipes = V/x + V/x+3 Volume of cistern filled in 40/13 min = 40/13 (V/x + V/x+3) Thus, 40/13 (V/x + V/x+3) = V Solve this to get the value of x and the required time.
- could you suggest a site for value based questions for class 10 board exam? Asked by:
**manisha** - Smita Kalra The sample papers with value based questions will soon be updated on the site www.topperlearning.com
- What type of questions can be asked from standard 9 chapter cirlces and for how many marks? Asked by:
**Geny** - Smita Kalra To look at the type of questions, you can practice the questions of this chapter from the sample papers available on the site www.topperlearning.com The unit 'Geometry' (Quadrilaterals, Area, Circles, Constructions) comes for 38 marks in the exams.
- How can i get topperpreboard papers for 11 class? Asked by:
**vandna** - Smita Kalra The board papers are for class 10 and 12.
- What happened about questions u r unable to solve I think alpha bita sums also I hv gone through ur quadratic eq videos Asked by:
**Rrc** - Smita Kalra Please let us know which question are you not able to solve.
- What r partial functions? Asked by:
**vandna** - Smita Kalra a partial function from X to Y is a function ƒ: X' → Y, where X' is a subset of X.
- the area of rhombus,the length of whose diagonals are 16cm and 24cm, is Asked by:
**pragya** - Smita Kalra Area of rhombus = 1/2 (Product of its diagonals) = 1/2 x 16 x 24 = 192 sq cm
- If AB = 12 cm, BC = 16 cm and AB BC, then radius of the circle passing through A,B and C is 6 cm 8 cm 10 cm 12 cm Asked by:
**Geny** - Smita Kalra There seems some mistake in your question. Please cross check and ask again.
- ANy example of value based quesion for 9th std . Or any site where we can get it ? Asked by:
**Saravanan** - Smita Kalra The sample papers with value based questions will soon be updated on the site www.topperlearning.com
- What questions r expected in 10th board papers Asked by:
**Rahul** - Smita Kalra You can practice the sample papers available on the site www.topperlearning.com. Once you do that you will definitely get an idea about the type of questions asked in the exam. Also, practice the past year papers also. I strongly Recommend Topper Preboards to you all: Register yourself for FREE on http://www.topperlearning.com/preboard First 10,000 registration will get FREE evaluation of their Answer Sheets as well.
- How to make the standard 9 chapter circles easy? Asked by:
**Geny** - Smita Kalra Get the basics right and practice the question bank available on the site www.topperlearning.com.
- What type of questions can be asked from the chapter relations and functions? Asked by:
**vandna** - Smita Kalra To know the probable questions, you can the practice the questions of this chapters available in the sample papers on the site www.topperlearning.com Also, I will strongly recommend you to attempt the topperpreboard papers.
- what are the area of trpezium Asked by:
**pragya** - Smita Kalra Half the sum of parallel sides x perpendicular distance between the parallel sides
- Q ) If the volume of a cube is 3root3a^3 , then TSA of the cube is a) 6 a^2 b) root3 a^2 c) 18 a ^2 d)18 root3 a^2 Asked by:
**Saravanan** - Smita Kalra Volume of the cube = (edge)^3 Put the given value in this formula to get the edge of the cube. TSA = 6(edge)^2
- will 9th std S.A 2 exam have value based question ? Asked by:
**Saravanan** - Smita Kalra Yes it will have.
- how to prepare after doing all exercises once each is we have to do sample paper or to do all exercises again Asked by:
**ansh** - Smita Kalra Understand the concepts thoroughly and practice all the exercises once and then you can attempt the sample papers in the time allotted.
- is optional exercises are not for 10th exam point of view as written or not Asked by:
**ansh** - Smita Kalra Generally, questions are not asked from the optional exercise. However, you should do those to improve on the concepts.
- what is difference b/w parabola and hyperbola in common language? Asked by:
**vandna** - Smita Kalra A parabola is the locus of a point, which moves in a plane in such a way that its distance from a fixed point (not on the line) in the plane is equal to its distance from a fixed straight line in the same plane. A hyperbola is the set of all points in a plane, the difference of whose distances from two fixed points in the plane is a constant. The two fixed points are called the foci of the hyperbola.
- if PSA paper of class 11(non-medical) will have hindi subject also? Asked by:
**vandna** - Smita Kalra Yes.
- if some extra qustions can also be asked from the chapter relations and functions (11)? Asked by:
**vandna** - Smita Kalra Extra questions can definitely come up in the exams. You can practice the extra questions available on the site www.topperlearning.com
- I am unable to solve quadratic equations of alpha bad bita sums Asked by:
**Rahul rc** - Smita Kalra You can look at the videos available on the site www.topperlearning.com to understand this topic well.
- is optional exercises are not important from 10th examination point of view as written Asked by:
**ansh** - Smita Kalra Generally, questions are not asked from the optional exercise. However, you should do those to improve on the concepts.
- if i require to do exersises of 10th clsses again or to solve sample paper after doing all exercises once Asked by:
**ansh** - Smita Kalra Understand the concepts thoroughly and practice all the exercises once and then you can attempt the sample papers in the time allotted.
- if some extra qustions can be asked from the chapter trigonometric functions (11)? Asked by:
**vandna** - Smita Kalra Extra questions can definitely come up in the exams. You can practice the extra questions available on the site www.topperlearning.com
- What type of questions can come in 11 final exam from mathematical reasoning? Asked by:
**vandna** - Smita Kalra To answer the questions based on mathematical reasoning, it is required to clear up the basic concepts. Once you are clear, you can solve any question. To see the type of questions you can look at the questions that came up in the last 5 years. Also, you can practice the sample papers available on the site www.topperlearning.com
- ABC and ABC are two right triangles with common hypotenuse AC. Prove that angle CAD= angle CBD. Asked by:
**PALAK** - Smita Kalra Use angle sum property in triangle ABC and ADC to get angle BAC + angle CAB = 90 angle ACD + angle DAC = 90 Adding the above equations, we get, angle BCD + angle DAB = 180 But angle B + angle D = 180 We can see that quadrilateral ABCD is having sum of measures of opposite angles as 180°. So, it is a cyclic quadrilateral. Consider chord CD. We get angle CAD = angle CBD (angles in same segment are equal)
- how to derive a funtion upto infinte no ? Asked by:
**pratik baid** - Smita Kalra Your question is not clear. Please clarify so that we may answer this to the best of the ability.
- How do I improve my marks in 1 month any suggested way? Asked by:
**Sriram** - Smita Kalra Revise your concepts thoroughly and keep the problems given in the ncert on your tips. Together with the studies keep a check on what you eat and maintain a regular sleep pattern. A regular seven hours of sleep is mandatory for the body to function well. Keep all unimportant issues at bay. Be focused. Practice the questions of the past year papers. You can also practice the sample papers available on the site www.topperlearning.com
- I have got low marks in Pre-board. Some say you can improve only to extent of 10 marks from preboard to final . is that true? Asked by:
**Sriram** - Smita Kalra It depends on individual. If after your pre-boards, you become serious and set your aim then you can really score more. You should revise all the concepts properly. Practice all the question from the ncert book thoroughly and get your basics right. Be focused. Keep all unimportant issues at bay. Also, practice the questions of the past year papers. You can also practice sample papers available on the site www.topperlearning.com
- I find 3D very difficult to conceptualize and understand. How do I do it? Asked by:
**Raja** - Smita Kalra Please watch the videos available on the site www.topperlearning.com to understand 3D geometry well.
- What is the difference between a tangent and a secant? Asked by:
**Mini** - Smita Kalra Tangent: A tangent to a circle is a line that intersects the circle in exactly ONE point. Secant: A line that intersects a circle in TWO distinct points is called a secant of the circle.