Calculate the area of a rectangle if the first side is 1.5 cm long and the second is 2.1 times longer.

1. Find the length of the second side by multiplying the length of the first side by the difference in the lengths of the sides.

1.5 * 2.1 = 3.15 (cm) length of the second side.

2. Let’s calculate the area of a rectangle by multiplying the lengths of its sides, and then we’ll find the correct answer.

1.5 * 3.15 = 4.725 (cm2) area of the rectangle.

Correct answer: 4.725.