In a vehicle's repair shed, 3 men and 8 boys can do a piece of work in 15 days; 4 men and 9 boys can do the same work in 12 days. Then, 5 men and 5 boys can do double the amount of this work in :
Choose the correct choice
A) 20 days	B) 33 days	C) 24 days	D) 28 days	E) none of these

Rationale: explanation : solution : ( 3 * 15 ) men + ( 8 * 15 ) boys = ( 4 * 12 ) men + ( 9 * 12 ) boys 45 m + 120 b = 48 m + 108 b < = > 3 m = 12 b = > 1 m = 4 b . . ' . 3 m + 8 b = ( 3 * 4 ) b + 8 b = 20 b . 5 m + 5 b = ( 5 * 4 ) b + 5 b = 25 b . let the required number of days be x . now , more boys , less days ( ip ) more work , more days ( dp ) boys 25 : 20 } : : 15 : x work 1 : 2 . ' . ( 25 * 1 * x ) = ( 20 * 2 * 15 ) = > x = 40 * 15 / 25 = 24 . answer : c
Answer: C