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?
Image
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':
Image
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.