Trolley park
In a supermarket, there are two lines of tightly packed trolleys. What is the length of one trolley?
Age
14 to 16
Challenge level
Problem
In a supermarket, there are two lines of tightly packed trolleys. The first line has ten trolleys and is $2.9\text{m}$ long. The second line has twenty trolleys and is $4.9\text{m}$ long. What is the length of one trolley, in m?
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If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Student Solutions
Answer: 1.1 metres
After the first trolley, each new trolley just makes a 'gap':
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10 trolleys = 1 trolley + 9 gaps = 2.9 m
20 trolleys = 2.9 m + 10 gaps = 4.9 m
$\therefore$ 10 gaps = 2 m $\Rightarrow$ 1 gap = 20 cm
1 trolley + 9$\times$20 cm = 2.9 m
$\therefore$ 1 trolley is 1.1 m long.