Mrs Lim had some eggs. She used 1/5 of them for a cake and 1/2 of the remainder for tarts. She had 24 eggs left. How many eggs did she have at first?
Worked answer
- Draw the eggs as 5 equal units. The cake uses 1 unit, so 4 units remain.
- The tarts use 1/2 of the 4 units = 2 units. 2 units are left.
- 2 units = 24, so 1 unit = 12. At first: 5 units = 5 × 12 = 60 eggs.
Answer: 60 eggs
The mistake this question tests
Habit
Fraction of a remainder
You added 1/5 and 1/2 as if both were fractions of all the eggs. The tarts used half of what was left after the cake. The "whole" changed.
How to fix it at home →Wrong answers children often give:
- 80 Fraction of a remainder
- 240 Fraction of a remainder
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See the answer →Practise PSLE fractions until the mistakes stop.
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