A baker uses sugar and flour to make treats for a school fair.
- The baker used 38 kg of sugar for cupcakes and 16 kg of sugar for biscuits. How much sugar did the baker use altogether? Give your answer as a fraction in its simplest form.
- The baker has 18 kg of flour. He packs all of it into bags of 23 kg each. How many bags of flour does he fill?
Need a hint?
(a) Change both fractions so they have the same denominator before adding. (b) How many 23 kg bags can you make from each 1 kg? Or turn ÷ into × using the upside-down fraction.
Worked answer
- (a) The denominators are 8 and 6. A common multiple is 24, so use 24ths.
- 38 = 924 and 16 = 424.
- 924 + 424 = 1324. This cannot be simplified, so the baker used 1324 kg of sugar.
- (b) Number of bags = 18 ÷ 23.
- Dividing by 23 is the same as multiplying by 32: 18 × 32 = 54 ÷ 2.
- 54 ÷ 2 = 27, so he fills 27 bags.
The mistake this question tests
Simplest form in final fraction answers
In part (a) pupils often add the tops and the bottoms to get 414. In part (b) they often multiply 18 × 23 = 12 instead of dividing, forgetting that smaller bags give more bags than kilograms.
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