# DBT JRF 2020 — Question 43

Exam: DBT JRF 2020 · Section: A · Topic: Aptitude & Reasoning · Difficulty: Medium

## Question

Eight 3rd year students can finish an experiment in 15 days and eighteen 1st year students can complete the same experiment in 10 days. If all these students work together, in how many days will the experiment get completed?

## Options

- **A.** 7.67
- **B.** 6.67
- **C.** 6.00
- **D.** 6.33

## Answer

Option C

## Explanation

Rate of work done = fraction of experiment completed per day. Rate of 8 senior students = $\dfrac{1}{15}$ experiment/day. Rate of 18 junior students = $\dfrac{1}{10}$ experiment/day. Combined rate = $\dfrac{1}{15} + \dfrac{1}{10} = \dfrac{2}{30} + \dfrac{3}{30} = \dfrac{5}{30} = \dfrac{1}{6}$ experiment/day. Time taken = $\dfrac{1}{1/6} = 6.00$ days.

Source: https://mypyqbuddy.com/questions/eight-3rd-year-students-can-finish-an-experiment-6a05a8a02adafec470293211