Subject: General Aptitude · Chapter: Time and Work · Exam: 2011 · Marks: · Difficulty:
A and B together can do a job in 2 days; B and C can do it in 4 days; A and C in $2 \frac{2}{5}$ days. The number of days required for A to do the job alone is
(a)1
(b)3
(c)6
(d)12
Answer
Answer (as printed): B
Explanation
(A+B)'s 1 day's work $= \frac{1}{2}$; (B+C)'s 1 day's work $= \frac{1}{4}$; (A+C)'s 1 day's work $= \frac{5}{12}$. Adding, we get: 2 (A+B+C)'s 1 day's work $= \left(\frac{1}{2}+\frac{1}{4}+\frac{5}{12}\right) = \frac{7}{6}$ $\Rightarrow$ (A+B+C)'s 1 day's work $= \frac{7}{12}$. So, A's 1 day's work $= \frac{7}{12} - \frac{1}{4} = \frac{1}{3}$. $\therefore$ A alone can do the work in 3 days.
Explanation as extracted from the printed page; notation may be imperfect.