Time and Work – Shortcut & Tricks & Theory – Solve without Pen or Paper (Trick no. 2)
Trick/Theory:- If ‘A’ and ‘B’ complete a work in ‘X’ days and ‘A’ alone can complete the same work in ‘Y’days.
Then, ‘B‘ alone can complete the same work in XY/(Y-X) days.
Trick/Theory 2:- If ‘A’ and ‘B’ complete a work in ‘X’ days and ‘B’ alone can complete the same work in ‘Y’days.
Then ‘A‘ alone can complete the same work in XY/(Y-X) days.
So two theory are same. So let’s solve some time and work questions……
Q-1) A and B together can complete a piece of work in 15 days and A alone in 20 days. In how many days can A alone complete the work? a) 25 days b) 30 days c) 40 days d) 60 days
Solution:- Here A and B complete a piece of work in 15 (X) days,
and A alone complete the same work 20 (Y) days.
So now apply this time and work tricks:- B can complete the same work in XY/(Y-X) days.
Now Put, X=15 and Y=20
= XY/(Y-X) days
=15*20/(20-15) days
=15*20/5 days
=3*20 days
=60 days
Your answer d) 60 days. [B can complete the same work in 60 days.]