It is asking you to find the length of the longer side of the rectangle using the given ratio.
Let's practise
The lengths of the sides of a rectangle are drawn in the ratio 4:7
The perimeter of the rectangle is 121 cm
What is the length of the longer side?
cm
- Read the question and then read it again. What is it asking you to do?
Show me
- Identify the ratio of part to part.
Show me
4:7
- Think of ratio as parts or shares.
The perimeter is the sum of the four sides.
The shorter sides of the rectangle represent four parts of the total perimeter and the longer sides represent seven parts.
How many parts in total is the perimeter shared into?
Show me
4 + 7 = 11
There are 11 parts in total.
- Now calculate the length that each of these parts of the perimeter represent.
Show me
121 ÷ 11 = 11
So each part represents 11 cm.
- The two longer sides represent seven parts of the perimeter, but I have only been asked about the length of one of these sides. So divide the length of the two longer sides by 2.
Show me
11 × 7 = 77 cm 77 ÷ 2 = 38.5 cm
- What is your answer?
Check your working.
Show me
38.5 cm
The shorter sides are four parts of the perimeter, which is 11 × 4 = 44 cm.
44 cm + 77 cm = 121 cm