What is the area of a rectangle ABCD if its sides are 5: 7 and one side is 3 cm larger than the other?

If we take for a fact that one side of the rectangle = X, and the other = Y, then X / Y = 5/7.

It turns out that X = 5/7 * Y. Hence it follows that the side X <Y.

It is also known by hypothesis that Y – X = 3.

Let’s make the substitution and get the following:

Y – 5/7 * Y = 3.

2/7 * Y = 3.

Y = 3 * 7/2.

Y = 10 ½.

Then X = 10 ½ – 3 = 7 ½.

The area of the rectangle is equal to the product of the sides X * Y = 7 ½ * 10 ½ = 15/2 * 21/2 = 365/4 = 91 ¼.

Answer: the area of the rectangle is 91 ¼.