CBSE mathematics

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Question
CBSEENMA10009809

The length of shadow of a tower on the plane ground is 3 times the height of the tower. The angle of elevation of sun is

  • 450

  • 300

  • 600

  • 900

Solution

B.

300

                 WiredFaculty

Let AB be the tower and BC be its shadow. Let θ be the angle of elevation of the sun.

According to the given information,

BC = 3 AB     ..........(1)In ABC,tanθ = ABBC = AB3 AB = 13     [Using (1)]We know that tan 300 = 13 θ = 300 

Hence, the angle of elevation of the sun is 300.

Sponsor Area

Question
CBSEENMA10009810

If the area of a circle is equal to sum of the areas of two circles of diameters 10 cm and 24 cm, then the diameter of the larger circle (in cm) is

  • 34

  • 26

  • 17

  • 14

Solution

B.

26

Diameter of two circles are given as 10 cm and 24 cm.

Radius of one circle = r1 = 5 cm,  Radius of other circle = r2 = 12 cm.

According to the given information,

Area of the larger circle = π(r1)2 + π(r2)2                                    = π(5)2 + π(12)2                                    = π(25 + 144)                                    = 169π                                    = π(13)2

 Radius of the larger circle = 13 cm

Hence, the diameter of larger circle = 26 cm.

Question
CBSEENMA10009811

If the radius of the base of a right circular cylinder is halved, keeping the height the same, then the ratio of the volume of the cylinder thus obtained to the volume of original cylinder is

  • 1 : 2

  • 2 : 1

  • 1 : 4

  • 4 : 1

Solution

C.

1 : 4

Let the original radius and the height of the cylinder be r and h respectively.

Volume of the original cylinder = πr2hRadius of the new cylinder = r2Height of the new cylinder = hVolume of the new cylinder = πr22h = πr2h4Required ratio = Volume of the new cylinderVolume of the original cylinder =  πr2h4 πr2h = 14 = 1 : 4

Question
CBSEENMA10009812

Two dice are thrown together. The probability of getting the same number on both dice is:

  • 12

  • 13

  • 16

  • 112

Solution

C.

16

When two dice are thrown together, the total number of outcomes is 36.

favourable outcomes = { (1,1),  (2,2),  (3,3),  (4,4),  (5,5),  (6,6) }

 

 Required probability = Number of favourable outcomesTotal number of outcomes = 636 = 16

Question
CBSEENMA10009813

The coordinates of the point P dividing the line segment joining the points A(1, 3) and B(4, 6) in the ratio 2 : 1 are

  • ( 2, 4 )

  • ( 3, 5 )

  • ( 4, 2 )

  • ( 5, 3 )

Solution

B.

( 3, 5 )

It is given that the point P divides AB in the ratio  2 : 1.

Using the section formula, the coordinates of the point P are

 

 1x1 + 2x42 + 1 ,  1x3 + 2x62 + 1= 1 + 83, 3 + 123 = (3,5)

Hence, the coordinates of the point P are (3,5).