The sides of a rectangular field are in the ratio 3 : 4. If the area of the field is 9408 sq. m, the cost of fencing the field @ 25 paise per metre is	Choose one:
A) rs . 55.50
B) rs . 67.50
C) rs . 86.50
D) rs . 98.00
E) none of these

Rationale: solution let length = ( 3 x ) metres and breadth = ( 4 x ) metres . then , 3 x × 4 x = 9408 ⇔ 12 x 2 = 9408 ⇔ x 2 = 784 ⇔ x = 28 . so , length = 84 m and breadth = 112 m . perimeter = [ 2 ( 84 + 112 ) ] m = 392 m . ∴ cost of fencing = rs . ( 0.25 × 392 ) = rs . 98.00 . answer d
Answer: D