1)

Twelve children take sixteen days to complete a work which can be completed by eight adults in twelve days. Sixteen adults started working and after three days ten adults left and four children joined them. How many days will they take to complete the remaining work ?


A) 3

B) 4

C) 6

D) 8

E) 7

Answer:

Option C

Explanation:

$12$ children take $16$ days to complete the work.

$\Rightarrow$ $1$ child takes $16\times 12=192$ days to complete the work.

$\Rightarrow$ Work done by $1$ child in $1$ day $=\frac{1}{192}$

$8$ adults take $12$ days to complete the work.

$\Rightarrow$ $1$ adult takes $12\times 8=96$ days to complete the work.

$\Rightarrow$ Work done by $1$ adult in $1$ day $=\frac{1}{96}$.

$16$ adults worked for $3$ days

Work completed $=16\times\frac{1}{96}\times 3$ $=\frac{1}{2}$.

Remaining work $=1-\frac{1}{2}$ $=\frac{1}{2}$

The remaining work is done by $6$ adults and $4$ children

Work done in $1$ day $=6\times\frac{1}{96}+4\times\frac{1}{192}$ $=\frac{1}{16}+\frac{1}{48}$ $=\frac{1}{12}$.

Required days to complete the remaining work $=\frac{1}{2}\div\frac{1}{12}$ = 6 days.