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Pencils and erasers — 5 : 3 worth $27.50
A stationery shop sells pencils and erasers in the ratio of 5 pencils to 3 erasers. Each pencil costs $0.50, and each eraser costs $1. If the total value of all the pencils and erasers is $27.50, how many pencils and erasers are there altogether?
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The pattern behind it: Number × value
One batch repeats. Work out one batch, then multiply.
In this one. Fix one repeating batch from the ratio, find the value of that batch, then use the total value to find the number of batches.
How to spot it
Items are described as a fixed group or ratio that repeats, such as tiles following a pattern, snacks sold in a fixed mix, or a rate given per hour or per item.
Common mistake
Children start from the grand total instead of first working out what one batch is worth. In rate questions they also confuse a duration with a clock time.
Try one like it
Standard Buns and muffins — 3 : 5 worth $55 A bakery sells buns and muffins in the ratio of 3 buns to 5 muffins. Each bun costs $2, and each muffin costs $1. If the total val…The 33 problem patterns
All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.
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