M4maths Previous Puzzles

02 Mar 2010 Wall and Man?

A forms a wall in 10 days and B forms it in 15 days. A and B start the work of forming wall together
but after 2 days A leaves the work. How many days are required for making the remaining wall by B?

OPtion

(1) 6
(2) 9
(3) 8
(4) 10
(5) 12
(6) 15
(7) 16
(8) 20
(9) 5
(10) 4

Solution

One day work of A = 1/10
One day work of B = 1/15
One day work of A and B = 1/10 + 1/15
= 1/6
After 2 days of work remaining work = 1- (2*1/6) = 4/6
No. of days required by B for doing this work = (4/6) / (1/15)
= 10

Correct Option: 4 Best Solution (0)