10 men,working 6 hours a day can complete a work in 18 days.How many hours a day must 15 men work to complete the same work in 12 days ?
Choose the correct choice
A) 6 B) 7 C) 8 D) 9 E) 10
Solution   Let the required number of hours per day be x.   More men,Less hours per day (Indirect Proportion)   Less days,More hours per day (Indirect Proportion)   ∴ 15 × 12 × x = 10 × 18 × 6 ⇔ x = 10x18x6/15x12 = x= 6. 6nswer 6
<result>A</result>
10 men,working 6 hours a day can complete a work in 18 days.How many hours a day must 15 men work to complete the same work in 12 days ?