4 technicians plan to repair 416 computers in 16 days.
However, after repairing for 10 days, one of the technicians fell sick and could not continue.
The remaining computers are to be repaired by the other three technicians. Assuming that the technicians work at the same rate, calculate the total number of days needed for all 416 computers to be repaired. Answer ... days

1. Find the repair rate per technician per day.

Total technician-days planned:
$4 \times 16 = 64$
So the rate per technician per day is
$\frac{416}{64}=6.5$
computers per day.

2. Find the number of computers repaired in the first 10 days and the number remaining.

In 10 days, 4 technicians repair
$4 \times 10 \times 6.5 = 260$
computers.

Remaining computers:
$416-260=156$

3. Find the additional days needed by 3 technicians and hence the total number of days.

With 3 technicians, the daily repair rate is
$3 \times 6.5 = 19.5$
computers per day.

Time needed for the remaining computers:
$\frac{156}{19.5}=8$
days.

Total number of days:
$10+8=18$