Question : P and Q can do a work together in 30 days. Q and R can do the same work together in 24 days and R and P together in 20 days. They started the work together, but Q and R left after 10 days. How many more days will P take to finish the remaining work?
Option 1: 23
Option 2: 21
Option 3: 18
Option 4: 19
Correct Answer: 18
Solution : LCM of 30, 24 and 20 = 120 Total work = 120 units Efficiency of (P + Q) = $\frac{120}{30}=4$ units/day Efficiency of (Q + R) = $\frac{120}{24}=5$ units/day Efficiency of (R + P) = $\frac{120}{20}=6$ units/day Now, (P + Q) + (Q + R) + (R + P) = 4 + 5 + 6 ⇒ 2 (P + Q + R) = 15 ⇒ (P + Q + R) = $\frac{15}{2}$units/day One day work of (P + Q + R) = $\frac{15}{2}$ Ten day work of (P + Q + R) = $\frac{15}{2}\times10=75$ Remaining work = 120 – 75 = 45 Efficiency of P = efficiency of (P + Q + R) – efficiency of (Q + R) = $\frac{15}{2}-5$ = $\frac{5}{2}$ The remaining work done by P with an efficiency of $\frac{5}{2}$ = $\frac{45}{\frac{5}{2}}$ = 18 Hence, the correct answer is 18.
Result | Eligibility | Application | Selection Process | Cutoff | Admit Card | Preparation Tips
Question : P and Q together can do a work in 12 days. P alone can do the same work in 18 days. In how many days can Q alone complete two-thirds part of the same work?
Question : P and Q can do a piece of work in 14 days. Q and R together can do it in 21 days. If P is twice as good a workman as R, then in how many days Q alone can do the work?
Question : A and B together can complete a project in 10 days. They started together, but A left after 2 days and the remaining work was completed by B in 12 days. In how many days can A complete the entire work while working alone?
Question : A can do work in 12 days and B in 24 days. If they work together, in how many days will they finish the work?
Question : A can do a piece of work in 25 days, and B can do the same in 30 days. They work together for 5 days, how much of the work is left?
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile