Question

A contract is to be completed in 52 days and 125 identical robots were employed, each operational for 7 hours a day. After 39 days, five-seventh of the work was completed. How many additional robots would be required to complete the work on time, if each robot is now operational for 8 hours a day?

• A.
  7
• B.
  8
• C.
  14
• D.
  15

Answer 1

The correct option is A

7
$125\times 7\times 39=\frac{5}{7}W$

$W=47775\text{Robot hrs.}$

Left work
$=47775-125\times 7\times 39$
$=13650\text{Robot hrs.}$

$13\times x\times 8=13650$
$x=131.25$

Addition robot required
$=131.25-125$
$=6.25=7$