The width of the rectangle is a dm, which is 40% of its length. What is the area of this rectangle?

The first step is to represent the percentages as a fraction. To do this, divide the number of percent by one hundred.

40% = 40/100 = 0.4.

Let’s calculate what the length is, knowing that 0.4 of it is a decimetres. To do this, we must divide the number a by 0.4.

a / 0.4 cm.

Let’s calculate what the area of the rectangle is. To do this, multiply the length by the width.

S = a / 0.4 * a = a² / 0.4 cm².

Answer: a² / 0.4 cm².

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