The food in a camp lasts for 10 men for 20 days. If 30 more men join, how many days will the food last? Options: A) 8 days B) 4 days C) 5 days D) 10 days E) 17 days

Rationale: "one man can consume the same food in 10 * 20 = 200 days . 30 more men join , the total number of men = 40 the number of days the food will last = 200 / 40 = 5 days . answer : c"
Answer: C