Mei Ling's money jar contained 10-cent coins and 50-cent coins. There were 6 more 50-cent coins than 10-cent coins. The total amount of money in the jar was $15.60.
- How many coins were in the jar?
- Mei Ling spends all her 10-cent coins on a snack. How much money is left in the jar?
Need a hint?
In (a), write the number of 50-cent coins as 6 more than the number of 10-cent coins, then form one equation in cents. In (b), find the value of the 10-cent coins first, then subtract it from the total.
Worked answer
- (a) Let the number of 10-cent coins be n, so the number of 50-cent coins is n + 6.
- Total value in cents: 10n + 50(n + 6) = 1560, so 60n + 300 = 1560.
- 60n = 1260, so n = 21. There are 21 ten-cent coins and 27 fifty-cent coins.
- Total number of coins = 21 + 27 = 48.
- (b) Value of the 10-cent coins = 21 × 10 cents = 210 cents = $2.10.
- Money left = $15.60 − $2.10 = $13.50.
The mistake this question tests
Left out the units
Students often forget that the 50-cent coins are 6 more than the 10-cent coins, or subtract the number of coins instead of their value in dollars.
How to fix it at home →More PSLE whole numbers questions
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See the answer →Practise PSLE whole numbers until the mistakes stop.
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