Q.

Sita Devi wants to make a rectangular pond on the road side for the purpose of providing drinking water for street animals. The area of the pond will be decreased by 3 square feet if its length is decreased by 2 ft. and breadth is increased by 1 ft. Its area will be increased by 4 square feet if the length is increased by 1 ft. and breadth remains the same. Find the dimensions of the pond. 

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a

7 × 4 ft

b

9 × 5 ft

c

8 × 3 ft

d

7 × 5 ft

answer is A.

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Detailed Solution

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Let length of rectangular pond = x 

and breadth of rectangular pond = y 

Area of rectangular pond = xy 

According to question- 

(x - 2)(y + 1) = (xy - 3) 

xy + x - 2y -2 = xy -3 

x - 2y = -1  —-(1) 

(x + 1). y = (xy + 4) 

xy + y = xy + 4 

y  = 4 —(2) 

Putting value of  y in (1) 

x  - 2(4) = -1 

x  - 8 = -1 

x  = 7  

Length of rectangular pond = 7 ft. 

Breadth of rectangular pond = 4 ft. 

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