99
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 = $50100R$$50100R$

Original area =$R2$  and new area = $πR2$

$3πR24*1πR2*100$

Decrease in area = $πR22=πR24$ = 75%

Q:

Find the area of the trapezium, whose parallel sides are 12 cm and 10 cm, and distance between the parallel sides is 14 cm?

 A) 121 sq.com B) 154 sq.com C) 186 sq.com D) 164 sq.com

Explanation:

We know that,

Area of trapezium = 1/2 x (Sum of parallel sides) x (Distance between Parallel sides)

= 1/2 x (12 + 10) x 14

= 22 x 14/2

= 22 x 7

= 154 sq. cm

16 494
Q:

The length and the breadth of rectangular field are in the ratio of 8 : 7. If charges of the painting the boundary of rectangle is at Rs. 10 per meter is Rs. 3000. What is the area of rectangular plot?

 A) 5600 sq.m B) 1400 sq. m C) 4400 sq.m D) 3600 sq.m

Explanation:

Perimeter of the rectangle is given by 3000/10 = 300 mts

But we know,

The Perimeter of the rectangle = 2(l + b)

Now,

2(8x + 7x) = 300

30x = 300

x = 10

Required, Area of rectangle = 8x x 7x = 56 x 100 = 5600 sq. mts.

11 595
Q:

The perimeter of a rectangle whose length is 6 m more than its breadth is 84 m. What will be the area of the rectangle?

 A) 333 sq.mts B) 330 sq.mts C) 362 sq.mts D) 432 sq.mts

Explanation:

Let the breadth of the rectangle = b mts

Then Length of the rectangle = b + 6 mts

Given perimeter = 84 mts

2(L + B) = 84 mts

2(b+6 + b) = 84

2(2b + 6) = 84

4b + 12 = 84

4b = 84 - 12

4b = 72

b = 18 mts

=> Length = b + 6 = 18 + 6 = 24 mts

Now, required Area of the rectangle = L x B = 24 x 18 = 432 sq. mts

14 949
Q:

How many square units in 13 by 9?

 A) 13 B) 9 C) 117 D) 13/9

Explanation:

Number of square units in 13 by 9 is given by the area it forms with length and breadth as 13 & 9

Area = 13 x 9 = 117

Hence, number of square units in 13 by 9 is 117 sq.units.

13 2005
Q:

Square units 13 by 9 of an office area is

 A) 97 B) 117 C) 107 D) 127

Explanation:

Square units 13 by 9 of an office means office of length 13 units and breadth 9 units.

Now its area is 13x 9 = 117 square units or units square.

17 4542
Q:

Find the area of the square whose side is equal to the diagonal of a rectangle of length 3 cm and breadth 4 cm.

 A) 25 sq.cm B) 16 sq.cm C) 9 sq.cm D) 4 sq.cm

Explanation:

Given length of the rectangle = 3 cm

Breadth of the rectangle = 4 cm

Then, the diagonal of the rectangle

Then, it implies side of square = 5 cm

We know that Area of square = S x S = 5 x 5 = 25 sq.cm.

13 2393
Q:

The length of a class room floor exceeds its breadth by 25 m. The area of the floor remains unchanged when the length is decreased by 10 m but the breadth is increased by 8 m. The area of the floor is

 A) 5100 sq.m B) 4870 sq.m C) 4987 sq.m D) 4442 sq.m

Explanation:

Let the breadth of floor be 'b' m.

Then, length of the floor is 'l = (b + 25)'

Area of the rectangular floor = l x b = (b + 25) × b

According to the question,

(b + 15) (b + 8) = (b + 25) × b

2b = 120

b = 60 m.

l = b + 25 = 60 + 25 = 85 m.

Area of the floor = 85 × 60 = 5100 sq.m.

33 4050
Q:

The sides of a right-angled triangle are 12 cm, 16 cm, 20 cm respectively. A new right angle Δ is made by joining the midpoints of all the sides. This process continues for infinite then calculate the sum of the areas of all the triangles so made.

 A) 312 sq.cm B) 128 sq.cm C) 412 sq.cm D) 246 sq.cm