Question

Ashish can complete $2$ jobs in $21$ days. Ritu can complete $1$ job in $12$ days. In how many days will both of them complete $1$ job, if they work together ?

• A. $5$ days
• B. $5$ days $14$ hours
• C. $4$ days $10$ hours
• D. $4$ days

Answer 1

Answer: (B)

$5$ days $14$ hours

Job done by Ashish in $1$ day $=\frac{2}{21}$
Job done by Ritu in $1$ day $=\frac{1}{12}$

Job done by both of them when they work together for one day $=\frac{2}{21}+\frac{1}{12}$

$=\frac{8+7}{84}=\frac{15}{84}$
Job will be completed by them in $\frac{1}{15/84}$ days

$=\frac{84}{15}$ days

$=5$ days $14$ hours $24$ mins

Option B is correct.