A toy shop has 120 yo-yos and 180 spinning tops.
- Write the ratio of the number of yo-yos to the number of spinning tops in its simplest form.
- The shop orders more yo-yos and keeps the 180 spinning tops. The ratio of yo-yos to spinning tops becomes 5 : 3. How many yo-yos does the shop have now?
Need a hint?
In (a), divide both numbers by the same factor until no common factor is left. In (b), first find the value of 1 part from the spinning tops.
Worked answer
- (a) 120 : 180 = 2 : 3, after dividing both numbers by 60.
- (b) 3 parts of the ratio are 180 spinning tops, so 1 part = 180 ÷ 3 = 60.
- (b) 5 parts = 5 × 60 = 300 yo-yos.
The mistake this question tests
Simplest form in final fraction answers
Pupils often take 180 as the number of yo-yos, or multiply 180 by 3 and divide by 5 (giving 108) instead of finding the value of one part first.
How to fix it at home →Wrong answers children often give:
- 108 Stopped at one part in ratio
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See the answer →Practise PSLE ratio until the mistakes stop.
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