Question

A rectangle has a perimeter of 92cm and its length is 1cm more than twice its width.

Using the definition of perimeter write an equation for P in terms of L and W
Using the relationship given in the problem statement, write an equation for L in terms of W.

Answer 1

P = 2(L + W) = 2L + 2W (first part)

L = 2W + 1 (second part)

Explanation:

L = length of rectangle
W = width of rectangle
P = perimeter of rectangle = 2 * (L + W)
So P = 2(L + W) = 2L + 2W (1)

It is also given that length is 2 * width + 1

So we get the equation

L = 2W + 1 for L in terms of W (2)

This question does not ask you to compute L and W but if you wanted to do that use the following steps
Substitute for L from equation 2 to equation 1 giving
P = 2(2W+1) + 2W = 4W + 2 + 2W = 6W + 2

We know P = 92

So 6W + 2 = 92
Subtracting 2 from both sides we get 6W = 90
Dividing both sides by 6 gives us W = 15
and L = 2 * 15 + 1 = 31

We can check this by finding the perimeter from L and W
perimeter = 2(L+W) = 2(31 + 15) = 2 (46) = 92 which matches the data in the question

Answer 2

Answer: Width = 15cm

L = 31cm

Explanation:

P = 92 cm

L = 1 + 2W

P = 2L + 2W

P = 2(1+2W) + 2W

P = 2+4W+2W

P = 2 + 6W

92cm = 2 + 6W

subtract 2 on both sides to cancel the 2 on the right side.

90cm = 6W

W = 90/6

Width = 15cm

L = 1+2W

L = 1 + 30cm

L = 31 cm

Verification:

P = 2L+2W

P = 2(31)+2(15)

P = 62+30

P = 92cm

Hope I Helped!