Question

$15$ persons complete a work in $4$ days by working $6$ hours a day. How many days will it take to complete the work if $30$ persons work $4$ hours a day?

• A. $6$
• B. $8$
• C. $4$
• D. $3$

Answer 1

The correct option is D $3$

No of person is inversely proportional to the no of days.
Again, no of hours is inversely proportional to the no of days.
So, $15\times 4=k=5\times x$
$\Rightarrow x=12$; taking no of hours per day constant.
$15\times 4=k=30\times x$
$\Rightarrow x=2$; taking no of hours per day constant.
$2\times 6=4\times y$; taking no of persons constant.
$\Rightarrow y=3$