On a shelf there were 3 times as many storybooks as comic books. After 14 of the storybooks were lent out and 45 comic books were added, the number of storybooks and the number of comic books became the same. How many comic books were on the shelf at first?
Need a hint?
Write the storybooks left as a fraction of the storybooks at first, then compare with the comic books after 45 are added.
Worked answer
- Let each comic book count as 1 unit; storybooks at first = 3 units.
- After 14 of the storybooks leave, 34 of 3 units remain = 94 units.
- Comic books after 45 are added = 1 unit + 45 books.
- So 94 units = 1 unit + 45, which means 54 units = 45.
- 1 unit = 45 ÷ 54 = 36 books.
- Comic books at first = 36.
The mistake this question tests
Fraction of a remainder
Pupils often treat the storybooks as 3 units and subtract 1/4 of the total instead of taking 14 of the storybooks, or they forget that the comic books also go up by 45 before comparing.
How to fix it at home →More PSLE ratio questions
Devi, Ethan and Farah sold some bookmarks at a school book fair
See the answer →Structured · 4mHao, Priya and Siti sold some raffle tickets at a school carnival
See the answer →Structured · 3mAt a concert, there were 1004 children and adults at first
See the answer →Structured · 3mLin and Ravi each used the same amount of clay to make mugs and bowls
See the answer →Structured · 4mThere were some stamps in Album M and Album N
See the answer →MCQ · 1mWrite the ratio 12 : 18 in its simplest form
See the answer →Practise PSLE ratio until the mistakes stop.
Three PSLE questions, free, no sign-up. You’ll see exactly where the marks went. Then 7 days of everything for S$4.99.