Question

A can do a piece of work in $7$ days of $9$ hr each, and B can do it in $6$ days of $7$ hour. How long will they take to do it working together $\frac{42}{5}$ hr a day ?

• A. $3$ days
• B. $4$ days
• C. $4.5$ days
• D. None

Answer 1

The correct option is A $3$ days

Unit of work		Days	Hour		Total Work
2	A	7	9	63	126
3	B	6	7	42	(L.C>M of 63 and 46)

Time taken to complete the work by $A$ and $B$=$=\frac{126}{(2+3)\times \frac{42}{5}}$days.

$=\frac{126\times 5}{5\times 42}$days.

$=3$days.