38
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%

Explanation:

New radius = $\inline \fn_cm \frac{50}{100}R$$\inline \fn_cm \frac{R}{2}$

Original area =$\inline \fn_cm \tiny \prod R^{2}$  and new area = $\inline \fn_cm \tiny \prod(\frac{R}{2})^{2}=\frac{\prod R^{2}}{4}$

Decrease in area = $\inline \fn_cm \tiny \frac{3\prod R^{2}}{4}\times \frac{1}{\prod R^{2}}\times 100$ = 75%

Q:

An order was placed for the supply of a carpet whose breadth was 6 m and length was 1.44 times the breadth. What be the cost of a carpet whose length and breadth are 40% more and 25% more respectively than the first carpet. Given that the ratio of carpet is Rs. 45 per sq. m ?

 A) Rs. 4082.40 B) Rs. 1024.21 C) Rs. 2810.6 D) Rs. 3214

Explanation:

Length of the first carpet = (1.44)(6) = 8.64 cm

Area of the second carpet = 8.64(1 + 40/100) 6 (1 + 25/100)

= 51.84(1.4)(5/4) sq m = (12.96)(7) sq m

Cost of the second carpet = (45)(12.96 x 7) = 315 (13 - 0.04) = 4095 - 12.6 = Rs. 4082.40

2 48
Q:

What is the length of the longest pole which can be kept in a room 12 m long, 4 m broad and 3 m high  ?

 A) 13 m B) 14 m C) 15 m D) 16 m

Explanation:

the length of the longest pole which can be kept in a room 12 m long, 4 m broad and 3 m high is

=> $\inline \fn_jvn \small d^{2}=12^{2}+4^{2}+3^{2} = 13$ mts.

2 138
Q:

A class is 6 meters 24 centimeters in length and 4 meters 32 centimeters in width. Find the least number of square tiles of equal size required to cover the entire floor of the class room ?

 A) 115 B) 117 C) 116 D) 114

Explanation:

Length = 6 m 24 cm = 624 cm
Width = 4 m 32 cm = 432 cm
HCF of 624 and 432 = 48
Number of square tiles required = (624 x 432)/(48 x 48) = 13 x 9 = 117.

2 47
Q:

The edge of three cubes of metal is 3 m, 4 m and 5 m. They are melted and formed into a single cube. Find the edge of the new cube  ?

 A) 15 m B) 4 m C) 6 m D) 9 m

Explanation:

The edge of the new cube is = $\inline \fn_jvn \small 3^{3}+4^{3}+5^{3}$ = $\inline \fn_jvn \small a^{3}$ => a = 6 m.

1 52
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

Explanation:

Area = (l + b – d) d

= (80 + 60 – 10)10

=> 1300 sq.mts

=> 1300 x 3 = Rs.3900