1.  A and B can do a work in 8 days, B and C can do the same work in 12 days. A, B and C together can finish it in 6 days. A and C together will do it in :
A. 4 days
B. 6 days
C. 8 days
D. 12 days

Answer: Option C

Explanation:

(A + B + C)'s 1 day's work = 1 ;
6

(A + B)'s 1 day's work = 1 ;
8

(B + C)'s 1 day's work = 1 .
12

Therefore (A + C)'s 1 day's work
= ( 2 x 1 ) - ( 1 + 1 )
6 8 12
= ( 1 - 5 (
3 24
= 3
24
= 1 .
8

So, A and C together will do the work in 8 days.