Question

$A$ can do a piece of work in $12$ days. $B$ can do this work in $16$ days. $A$ started the work alone. After how many days should $B$ join him, so that the work is finished in $9$ days?

• A. $5$
• B. $4$
• C. $3$
• D. $2$

Answer 1

The correct option is A $5$

$A^{\prime }s$ work in $9$ days $=\frac{9}{12}=\frac{3}{4}$
Remaining work $=\frac{1}{4}$
Remaining work was done by $B$ in
$=\frac{1}{4}\times 16=4$ days.
$\therefore B$ should join $A$ after $9-4=5$ days.