A group of 5 students can read a 400-page book in 8 days, working 4 hours per day. How many days will 10 students, working 5 hours per day, take to read the same book?

hard 4 marks Class 8 · Mathematics · Direct and Inverse Proportions

Answer

3.2 days

The correct answer is 3.2 days — Divide total pages by daily capacity: $400 d i v 125 = 3.2$ days.

Step-by-step solution

Compute reading rate per student-hour: $400 \div (5 \times 4 \times 8) = 2.5$ pages/student‑hour.
Calculate daily capacity of new team: $10 \times 5 \times 2.5 = 125$ pages/day.
Divide total pages by daily capacity: $400 d i v 125 = 3.2$ days.

Common mistake: Ignoring hours per day or miscalculating total hours

Concept tested: Inverse proportion with workers, hours, and time