Question 14

Explanation

To solve this efficiently, we use the concept of work rate, where rate is inversely proportional to time. Let the work rates of each person be $v_A$, $v_B$, and $v_C$.

Based on the problem, we can set up three combined rate equations:

Instead of finding each value individually, we can sum all three equations. Notice that each variable appears twice.

From the equation above, we get their total combined work rate:

Since the total work rate is $\frac{1}{10}$ of the job per day, the time required to complete 1 full job is the reciprocal.

Thus, they need $10$ days.