151
Q:

If the radius of a circle is decreased by 50%, find the percentage decrease in its area.

A) 55% B) 65%
C) 75% D) 85%

Answer:   C) 75%



Explanation:

Let original radius = R. 

 

New radius = 50100R50100R 

 

Original area =R2  and new area = πR2

 

3πR24*1πR2*100 

 

Decrease in area = πR22=πR24 = 75%

Q:

Chords AB and CD of a circle intersect at a point P inside the circle. If AB = 10 cm, AP = 4 cm and PC = cm, then CD is equal to:

 

A) 4.8 cm B) 9.8 cm
C) 7.8 cm D) 6.8 cm
 
Answer & Explanation Answer: B) 9.8 cm

Explanation:
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0 16
Q:

Triangle  ABC ~ Triangle RQP and PQ = 10 cm, QR = 12 cm and RP = 16 cm. If ar( triangle PQR): ar ( triangle  ABC) =  9/4 , then BC is equal to:

 

A) 8 cm B) 6 cm
C) \frac{20}{3} cm D) \frac{32}{3} cm
 
Answer & Explanation Answer: C) \frac{20}{3} cm

Explanation:
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0 41
Q:

In triangle ABC, P is a point on BC such that BP : PC = 2 : 3 and Q is the mid point of AP. Then ar(triangle ABQ): ar(triangle ABC) is equal to:

 

A) 1:5 B) 1:4
C) 2:3 D) 2:5
 
Answer & Explanation Answer: A) 1:5

Explanation:
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0 22
Q:

In a circle with centre O, AB is a diameter and CD is a chord such that ABCD is a trapezium. If angle BAC = 28 deg, then angle CAD is equal to:

 

A) 32^\circ B) 62^\circ
C) 34^\circ D) 28^\circ
 
Answer & Explanation Answer: C) 34^\circ

Explanation:
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0 46
Q:

A sphere of radius 4 cm is melted and recast into smaller spheres of radii 2 cm each. How many such spheres can be made?

 

 

A) 8 B) 32
C) 4 D) 16
 
Answer & Explanation Answer: A) 8

Explanation:
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1 28
Q:

Triangle ABC ~ Triangle EDF and ar(ABC) : ar(DEF) = 4 : 9. If AB = 6 cm, BC = 8 cm and AC = 10 cm, then DF is equal to:

A) 9 cm B) 12 cm
C) 15 cm D) 18 cm
 
Answer & Explanation Answer: B) 12 cm

Explanation:
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0 26
Q:

In a circle of radius 13 cm, a chord is at a distance of 12 cm from the centre of the circle. What is the length of the chord?

 

A) 5 cm B) 10 cm
C) 7 cm D) 9 cm
 
Answer & Explanation Answer: B) 10 cm

Explanation:
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0 62
Q:

In the given figure, AP bisects angle BAC. If AB = 4 cm, AC = 6 cm and BP = 3 cm, then the length of CP is:

 

 

A) 3 cm B) 7 cm
C) 5 cm D) 4.5 cm
 
Answer & Explanation Answer: D) 4.5 cm

Explanation:
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2 187