The width of the rectangle is 63cm. How much the area of the rectangle will decrease if its length is reduced by 4 cm.

Let us express the area of ​​a rectangle with a width of 63 cm (b = 63 cm):
S1 = a * b = 63 * a.

Let us express the area of ​​a rectangle with a length reduced by 4 cm and a width equal to 63 cm:
S2 = a * b = (a – 4) * 63 = 63 * a – 252.

To determine by how many units one quantity is greater (or less) than another, it is necessary to subtract another from one quantity.
If the difference is greater than 0, then the first value is greater than the second; if the difference is less than 0, then the first value is less than the second; if the difference is 0, then both values ​​are equal.

Let’s calculate how much S2 is less than S1:

S1 – S2 = 63 * a – (63 * a – 252) = 63 * a – 63 * a + 252 = 252.

Since S1 is more than S2 by 252 units ^ 2, then, accordingly, S2 is 252 units ^ 2 less than S1.

Answer: the area of ​​the rectangle will decrease by 252 units ^ 2.