3 men and 4 boys can earn ` 756 in 7 days. 11 men and 13 boys can earn ` 3008 in 8 days. In what time will 7 men with 9 boys earn ` 2480?
(a)8 days
(b)9 days
(c)10 days
(d)11 days
Answer
Answer (as printed): C
Explanation
Let 1 man's daily earning be ` x and 1 boy's daily earn- ing be ` y. 756 Then, 3x + 4y = = 108 ...(i) 7 3008 And, 11x + 13y = = 376 ...(ii) 8 Multiplying (i) by 11 and (ii) by 3, we get: 33x + 44y = 1188 ...(iii) 33x + 39y = 1128 ...(iv) Subtracting (iv) from (iii), we get: 5y = 60 or y = 12. Putting y = 12 in (i), we get: 3x = 60 or x = 20. \ Required time 2480 2480 2480 = = = = 10 days. 7 x + 9 y 7 × 20 + 9 × 12 248
Explanation as extracted from the printed page; notation may be imperfect.