Question

Ram can finish a work in $45$ minutes. His son can finish a work in $3$ hours. If they work together, how long will it take them to finish the work?

• A. $24$ minutes
• B. $30$ minutes
• C. $36$ minutes
• D. $40$ minutes

Answer 1

Answer: (C)

$36$ minutes

Ram can finish a work in $45$ minute

$\therefore$ work done by Ram in $1$ minute $=$ $\frac{1}{45}$

Ram's son can finish a work in $3$ hr $=180$ minute

$\therefore$ Work done by his son in $1$ minute $=\frac{1}{180}$

If they work together then work done by both in $1$ minute

$=\frac{1}{45}+\frac{1}{180}$

$=\frac{4+1}{180}=\frac{5}{180}=\frac{1}{36}$

Then it will take $36$ minute if they work together.