Question

A can do a work in
15 days and B
in 20 days. If they work it together
for 4 day, then the fraction of the
work that is left is​

Answer 1

Given

• A can do a peice of work in 15days

• B can do the piece of work in 20days

• if they work together for 4days

To find

• The rest of work left after 4 days in fraction

Solution

For A

• A can do a peice of work in 15day

• In one day A do 1/15 peice of work

For B

• B can do a peice of work in 20day

• dayIn one day B do 1/20 peice of work

If they work together

$\rightarrow\tt{\dfrac{1}{A}+\dfrac{1}{B}}$

$\rightarrow\tt{\dfrac{1}{15}+\dfrac{1}{20}}$

$\rightarrow\tt{\dfrac{4+3}{60}}$

$\rightarrow\tt{\dfrac{7}{60}}$

$\rightarrow\tt{\dfrac{60}{7}}$

Now work left

Work left = the days of work to complete work - work for 4 days

According to the question

• they work it together
• for 4 day

Work left = 60/7 - 4

work left = (60-28)/4

work left = (32)/4

work left = 8