Seema reads 1/5 of a book per hour. If she goes to sleep after reading the…
2016
Seema reads 1/5 of a book per hour. If she goes to sleep after reading the book for 2 1/3 hours, how much part of the book is left to be read?
- A.
8/15
- B.
7/15
- C.
3/7
- D.
1/5
Attempted by 6 students.
Show answer & explanation
Correct answer: A
When something is done at a constant rate, the fraction of the task finished after a given time equals rate × time, and the fraction still remaining is (1 − fraction finished). Any mixed number of hours must first be rewritten as an improper fraction before it is multiplied by the rate.
Convert the time Seema reads into an improper fraction: 2 1/3 hours = (2 × 3 + 1)/3 = 7/3 hours.
Multiply the rate by the time to get the fraction of the book she has read: 1/5 × 7/3 = 7/15.
Subtract the fraction read from the whole book (1) to get the fraction left to read: 1 − 7/15 = 15/15 − 7/15 = 8/15.
Check: the read portion and the remaining portion must add up to the whole book — 7/15 + 8/15 = 15/15 = 1. So 8/15 of the book is confirmed as the part still left to be read.
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