Overview Exercise "When ambition ends, happiness begins."
- (Proverb)
11.
The difference between the length and breadth of a rectangle is 23 m. If its perimeter is 206 m, then its area is:
A. 1520 m2 B. 2420 m2 C. 2480 m2 D. 2520 m2
Answer: D
Explanation:
We have: (l - b ) = 23 and 2(l + b ) = 206 or (l + b ) = 103.
Solving the two equations, we get: l = 63 and b = 40.
l x b ) = (63 x 40) m2 = 2520 m2 .
12.
The length of a rectangle is halved, while its breadth is tripled. What is the percentage change in area?
A. 25% increase B. 50% increase C. 50% decrease D. 75% decrease
Answer: B
Explanation:
Let original length = x and original breadth = y .
Original area = xy .
New breadth = 3y .
New area =
x x 3y
=
3
xy .
2
2
1
xy x1
x 100
= 50%.
2
xy
13.
The length of a rectangular plot is 20 metres more than its breadth. If the cost of fencing the plot @ 26.50 per metre is Rs. 5300, what is the length of the plot in metres?
A. 40 B. 50 C. 120 D. Data inadequate E. None of these
Answer: D
Explanation:
Let breadth = x metres.
Then, length = (x + 20) metres.
Perimeter =
5300
m = 200 m.
26.50
x + 20) + x ] = 200
x + 20 = 100
x = 80
x = 40.
Hence, length = x + 20 = 60 m.
14.
A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered. If the area of the field is 680 sq. feet, how many feet of fencing will be required?
Answer: E
Explanation:
We have: l = 20 ft and lb = 680 sq. ft.
So, b = 34 ft.
l + 2b ) = (20 + 68) ft = 88 ft.
15.
A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:
A. Rs. 456 B. Rs. 458 C. Rs. 558 D. Rs. 568
Answer: D
Explanation:
Area to be plastered
= [2(l + b ) x h ] + (l x b )
= {[2(25 + 12) x 6] + (25 x 12)} m2
= (444 + 300) m2
= 744 m2 .
744 x
75
= Rs. 558.
100
Area = (l x b) = (63 x 40) m2 = 2520 m2.
2x + 20 = 100