1000 men have provisions for 21 days. If 800 more men join them, for how many days will the provisions last now?	Select.
A) 12.9  B) 12.5  C) 12.6  D) 11.6  E) 12.1

Rationale: "1000 * 21 = 1800 * x x = 11.6 answer : d"
Answer: D