Dina and Kai had the same amount of money at first. At a school fair, Dina bought 1 sandwich and 2 cups of juice and had $6 left. Kai wanted to buy 4 sandwiches and 2 cups of juice, but he was short of $24. A cup of juice costs $4.
- How much does one sandwich cost?
- How much money did Dina have at first?
Need a hint?
Both children have the same money, and Kai wants 3 more sandwiches than Dina. What does the gap between 'left over' and 'short of' pay for?
Worked answer
- (a) Kai wanted 3 more sandwiches than Dina (4 − 1 = 3). The juice is the same.
- Dina had $6 left, but Kai was short of $24, so the gap between them is $6 + $24 = $30.
- This $30 is the cost of 3 sandwiches, so 1 sandwich costs $30 ÷ 3 = $10.
- (b) Dina spent $10 on 1 sandwich and 2 × $4 = $8 on juice, which is $18 altogether.
- Money at first = $18 + $6 left = $24.
Answer: $24
The mistake this question tests
Habit
Calculation slip
Many pupils subtract $24 − $6 instead of adding, because they forget that one child has money left over and the other is short. The gap between them is $6 + $24.
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