Multiple choice

A is 50% more efficient than B and C is 40 % less efficient than B. Working together they can complete a task in 10 days . in how many days will A alone complete 150% of the work?

  1. 32

  2. 35

  3. 31

  4. 40

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let B's efficiency be 100 units/day. Then A's efficiency is 150 (50% more) and C's efficiency is 60 (40% less). Combined efficiency = 150+100+60=310 units/day. Total work = 310×10=3100 units. A alone does 150% of 3100 = 4650 units. At 150 units/day, A needs 4650/150=31 days. If A took 35 days, efficiency would need to be about 133 units/day, not 150.