In this question, all lengths are in centimetres - OCR - GCSE Maths - Question 24 - 2019 - Paper 1

Question 24

In this question, all lengths are in centimetres.
Here is a square.
4a + 2b
6a + b - 1
Find the length of one side of the square when b = 4.
Worked Solution & Example Answer:In this question, all lengths are in centimetres - OCR - GCSE Maths - Question 24 - 2019 - Paper 1
Substituting b = 4

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Start by substituting the value of b into the expressions for the side length.
For the left side, substituting gives us:
4a+2(4)=4a+8
For the top side:
6a+(4)−1=6a+3
Setting the sides equal

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Since both expressions represent the length of a side of the square, we set them equal to each other:
4a+8=6a+3
Solving for a

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To solve for a, rearrange the equation:
4a+8−3=6a
This simplifies to:
5=6a−4a
5=2a
Now divide both sides by 2:
a = rac{5}{2} = 2.5
Finding the length of one side

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Finally, substitute a back into one of the expressions to find the length of one side of the square:
Using the expression for the left side:
4(2.5)+8=10+8=18
Thus, the length of one side of the square is 18 cm.
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