Question: B and C together can complete a work in 8 days. A and B together can complete the same work in 12 days and A and C together can complete the same work in 16 days. In how many days can A, B and C together complete the same work?
Options:
A) $ 3\frac{9}{13} $
B) $ 7\frac{5}{13} $
C) $ 7\frac{5}{12} $
D) $ 3\frac{5}{12} $
E) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
- (B + C)’s 1 day’s work $ =\frac{1}{8} $ (i)
(A + B)‘s1 day’s work $ =\frac{1}{12} $ … (ii)
(A + C)’s 1day’s work $ =\frac{1}{16} $ … (iii)
On adding Eqs. (i), (ii) and (lii), we get
2 (A + B + C)’s 1 day’s work
$ =\frac{1}{8}+\frac{1}{12}+\frac{1}{16}=\frac{6+4+3}{48}=\frac{13}{48} $
$ \Rightarrow $ (A + B + C)’s 1 day’s work $ =\frac{13}{96} $
$ \therefore $ A, B and C together can complete the work in
$ =\frac{96}{13}=7\frac{5}{13}days $