SSC Sample Paper Mock Test-15 SSC CGL Tear-II Paper-1

If A and B together can finish a piece of work in 20 days, B and C in 10 days and C and A in 12 days, then A, B and C jointly can finish the same work in

A) \[4\frac{2}{7}\text{days}\]

B) 30 days

C) \[8\frac{4}{7}\text{days}\]

D) \[\frac{7}{10}\text{days}\]

Correct Answer: C

Solution :

(A + B)'s day work \[=\frac{1}{20}\]

(B + C)'s 1 day work \[=\frac{1}{10}\]

(C + A)'s 1 day work \[=\frac{1}{12}\]

2 (A + 5 + C)'s 1 day work \[=\frac{1}{20}+\frac{1}{10}+\frac{1}{12}\]

\[=\frac{3+6+5}{60}=\frac{14}{60}=\frac{7}{30}\]

\[\therefore \] (A+B+C)'s 1 day work\[=\frac{7}{30}\times \frac{1}{2}=\frac{7}{60}\]

Hence, A, B and C can finish the work together in\[\frac{60}{7}\]days or \[8\frac{4}{7}\]days.