Question

A rectangle with dimensions of 3 units by 7 units is enlarged by a scale factor of 1.1. By what percent does it’s area increase?

Answer 1

Answer:

$21\%$

Step-by-step explanation:

Original dimensions of the rectangle

$l=7\ \text{units}$

$w=3\ \text{units}$

Area of the rectangle

$A=7\times 3=21\ \text{units}^2$

Scale factor = 1.1

New dimensions

$l'=7\times 1.1=7.7\ \text{units}$

$w'=3\times 1.1=3.3\ \text{units}$

The new area of the rectangle

$A'=7.7\times 3.3=25.41\ \text{units}^2$

Percentage change is given by

$\dfrac{A'-A}{A}\times 100\\ =\dfrac{25.41-21}{21}\times 100=21\%$

The percentage by which the area of the rectangle increases is $21\%$.