A is thrice as efficient as B, and B is twice as efficient as C. If A, B and C work together, how long will they take to complete a job which B completes in 10 days ?

Foundation

Mathematics Foundation

Ratio Proportion

Time Speed Distance

Direct and Inverse Proportions

Question

A is thrice as efficient as B, and B is twice as efficient as C. If A, B and C work together, how long will they take to complete a job which B completes in 10 days ?

A

$\frac{11}{9}$ days

B

3 days

C

None of these

D

$\frac{20}{9}$ days

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B takes 10 days to finish the job

⇒ A will take $\frac{10}{3}$ days to finish it.

⇒ C will take 20 days to finish it.

Together they will finish the work in

$\frac{1}{\frac{1}{10} + \frac{1}{20} + \frac{3}{10}} = \frac{20}{9}$ days