Question

if 20 girls can complete 1/3 of work in 20 days , how many more girls should be employed to finish the rest of the work in 25 days

Answer 1

20 girls complete in 20 days 1/3 work
1 girl complete in 20 days 1/60 work
1 girl complete in 1 day 1/1200 work

now 1 day 1/1200 work is completed by 1 girl
in 25 day 25/1200 work completed by 1 girl
in 25 day whole work is completed by
1/(25/1200) girls=48 girls