36
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 = 

Original area =  and new area = 

Decrease in area =  = 75%

Q:

A rectangular lawn of dimensions 80 m x 60 m has two roads each 10 m wide running in the middle of the lawn, one parallel to the length and the other parallel to the breadth. What is the cost of traveling the two roads at Rs.3 per sq m ?

A) Rs. 3600 B) Rs. 3800
C) Rs. 3900 D) Rs. 3700
 
Answer & Explanation Answer: C) Rs. 3900

Explanation:

Area = (l + b – d) d

= (80 + 60 – 10)10

=> 1300 sq.mts

=> 1300 x 3 = Rs.3900

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1 48
Q:

The ratio between the length and breadth of a rectangular field is 5 : 4 if the breadth is 20m less than the length, the perimeter of the field is :

A) 260m B) 280m
C) 360m D) none of these
 
Answer & Explanation Answer:

Explanation:
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5 209
Q:

If a 36 cm thread is used to wrap a book, lengthwise twice and breadth wise once, what is the size of the book ?

A) 288 sq.cm B) 188 sq.cm
C) 144 sq.cm D) 244 sq.cm
 
Answer & Explanation Answer: A) 288 sq.cm

Explanation:

Length of the thread is 36 cms.
length wise twice breath wise once then totally thrice.
so 36/3 = 12.
so length is 12 x 2 = 24 cms
breath is 12 cms
Area of the book = length x breath = 24 x 12 = 288 sq.cm

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2 139
Q:

If 4 circles of equal radius are drawn with vertices of a square as the centre , the side of the square being 7 cm, find the area of the circles outside the square ?

A) 119.21 sq cm B) 115.395 sq cm
C) 104.214 sq cm D) 111.241 sq cm
 
Answer & Explanation Answer: B) 115.395 sq cm

Explanation:

Because each vertice of the square is the center of a circle
(1/4) part of the total area of each circle inside of the square.
(3/4) part of the total area of each circle outside of the square.
Thus total area outside the square is = 115.3955 sq cm.

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2 131
Q:

What is the least number of squares tiles required to pave the floor of a room 15 m 17 cm long and 9 m 2 cm broad ?

A) 844 B) 814
C) 840 D) 820
 
Answer & Explanation Answer: B) 814

Explanation:

Length of largest tile = H.C.F. of 1517 cm and 902 cm = 41 cm.
Area of each tile = (41 x 41) sq.cm

Required number of tiles =1517 x 902/(41 x 41) = 814.

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4 329