IBPS PO Prelims Model Paper 9 with solutions

A can do the work in 5 days, so he can do 20% work in 1 day.
B can do the work in 4 days. So he can do 25% work in 1 day.
So, together they can do = 20 + 25 = 45% work in 1 day.
The work is increased by 800%.
So the work becomes 900%.
Therefore work can be done by both A and B in =

900

45

= 20 days.