Rectangle area

The length of a rectangle is x units, and the width is y. Dimensions are increased by 10% and 15%, respectively. What is the ratio of the areas of the old and new rectangle?

Correct answer:

r =  1.265
p =  26.5 %

Step-by-step explanation:

$$\begin{gathered} a_2=1.10a_1 \\ {b}_2=1.15b_1 \\ {S}_1=a_1\cdot b_1 \\ {S}_2=a_2\cdot b_2=1.10a_1\cdot 1.15b_1 \\ {S}_2=1.10\cdot 1.15\cdot S_1 \\ r=1.10\cdot 1.15=1.265 \end{gathered}$$

$p=100\cdot (r-1)=100\cdot (1.265-1)=26.5\%$

Try another example