Roller-skating race — Kai and Mia
Kai and Mia took part in a roller-skating race. Kai skated at a constant speed of 18 km/h. Both skaters kept the same speed throughout the race. When Mia had covered of the distance, Kai was 2.7 km ahead of her. Kai reached the finishing line at 8.52 a.m. What time did Mia reach 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. Double the entire halfway snapshot: constant speeds mean that when Mia's distance doubles to the whole race, Kai's 2.7 km extra distance also doubles to 5.4 km.
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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