Aptitude Discussion

Q. |
$A$, $B$ and $C$ can do a work in 5 days, 10 days and 15 days respectively. They started together to do the work but after 2 days $A$ and $B$ left. $C$ did the remaining work (in days) |

✖ A. |
1 |

✖ B. |
3 |

✖ C. |
5 |

✔ D. |
4 |

**Solution:**

Option(**D**) is correct

If $A$, $B$ and $C$ work together for a day then they will finish

\(\left(\dfrac{1}{5}+\dfrac{1}{10}+\dfrac{1}{15}\right)^{th}\)work = \(2\times \dfrac{11}{30}=\left(\dfrac{11}{15}\right)^{th}\)work

Therefore working together for two days they will finish

$C$ alone does remain \(\left(\dfrac{11}{15}-1\right)=\left(\dfrac{4}{15}\right)^{th}\) work

But $C$ finishes \(\left(\dfrac{1}{15}\right)^{th}\)work in one day

Therefore $C$ will finish \(\left(\dfrac{4}{15}\right)^{th}\)work in **4 days.**