Kayaking race — Ben and Farah
Ben and Farah took part in a kayaking race. Ben paddled at a constant speed of 24 km/h. Both of them did not change their speed throughout the race. When Farah had covered of the distance, Ben was 3 km in front of her. Ben crossed the finishing line at 9.20 a.m. What time did Farah cross the finishing line?
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The pattern behind it: Units and parts
Cut one amount into equal shares. One number tells you what a share is worth.
In this one. Compare the time each racer needs for one half: Ben's 3 km lead converts into a 7.5-minute gap, and constant speeds make that same gap occur again in the second half.
Also uses: Same time, same distance
How to spot it
A single amount is split by a ratio, a fraction or a percentage. One extra number gives you the leftover, the difference, or the value of one share.
Common mistake
Children match the given number to the wrong number of shares, using the whole bar when the number covers only the leftover or the difference between two people's shares.
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Standard A bicycle's price — the percentage increase A bicycle shop increased the price of a bicycle from $650 to $780. What is the percentage increase?The 33 problem patterns
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