If 4 men working 10 hours a day earn Rs. 1600 per week, then 9 men working 6 hours a day will earn how much per week?	Select.
A) rs 840  B) rs 1320  C) rs 1620  D) rs 2160  E) none of these

Rationale: "explanation : ( men 4 : 9 ) : ( hrs / day 10 : 6 ) : : 1600 : x hence 4 * 10 * x = 9 * 6 * 1600 or x = 9 * 6 * 1600 / 4 * 10 = 2160 answer : d"
Answer: D