Here are two squares, A and B - Edexcel - GCSE Maths - Question 15 - 2020 - Paper 2

The area of square A is given by the formula for the area of a square, which is side length squared:

$A_A = x^2$

The area of square B is:

$A_B = (x + 4)^2$

According to the problem, we know that:

$(x + 4)^2 = x^2 + 70$

Expanding the left side gives us:

$x^2 + 8x + 16 = x^2 + 70$

Now, simplify the equation by eliminating $x^2$ from both sides:

$8x + 16 = 70$

Subtract 16 from both sides:

$8x = 54$

Dividing both sides by 8 gives:

$x = 6.75$

Now that we know the side length of square A, we can find the length of square B:

$B = 6.75 + 4 = 10.75 ext{ cm}$

Now, calculate the area of square B:

$A_B = (10.75)^2 = 115.5625 ext{ cm}^2$

Rounding to 3 significant figures gives:

$A_B = 116 ext{ cm}^2$