X is twice as good as Y and Y is twice as good as Z while doing a task. If X and Y can complete the task in 4 days, then how many days will z take to complete that task himself only.
Answer & explanation
Correct answer: option 4
X : Y : Z
Efficiency: 4 : 2 : 1
Now,
X + Y : Z
Efficiency: 6 : 1
Time : 1 : 6
ATQ,
(X + Y )1R = 4 days
Therefore, Z alone will do in = 6R = 6 × 4 = 24 days