45 men working 8 hours per day dig 30 m deep. How many extra men should be put to dig to a depth of 50 m working 6 hours per day? Choose one.
A) 17  B) 97  C) 18  D) 55  E) 72

Rationale: "( 45 * 8 ) / 30 = ( x * 6 ) / 50 = > x = 100 100 – 45 = 55 answer : d"
Answer: D