Subject: General Aptitude · Chapter: Time and Work · Exam: 2008 · Marks: · Difficulty:
A can build a wall in the same time in which B and C together can do it. If A and B together could do it in 25 days and C alone in 35 days, in what time could B alone do it?
(a)90 days
(b)100 days
(c)175 days
(d)None of these
Answer
Answer (as printed): C
Explanation
(A+B)'s 1 day's work $=\frac{1}{25}$; C's 1 day's work $=\frac{1}{35}$. (A+B+C)'s 1 day's work $=\left(\frac{1}{25}+\frac{1}{35}\right)=\frac{12}{175}$ ...(i). Also, A's 1 day's work = (B+C)'s 1 day's work ...(ii). From (i) and (ii), we get: $2 \times$ (A's 1 day's work) $=\frac{12}{175} \Rightarrow$ A's 1 day's work $=\frac{6}{175}$. $\therefore$ B's 1 day's work $=\frac{1}{25}-\frac{6}{175}=\frac{1}{175}$. So, B alone can do it in 175 days.
Explanation as extracted from the printed page; notation may be imperfect.