Sides of a rectangle

The dimensions of a rectangle are in a 4:12 ratio. If the shorter side length is 12 cm, what is the length of the longer side in centimeters?

Correct answer:

b =  36 cm

Step-by-step explanation:

$$\begin{gathered} a=12\text{cm} \\ a:b=4:12 \\ b:a=12:4 \\ b=a\cdot \frac{12}{4}=12\cdot \frac{12}{4}=\frac{12\cdot 12}{4}=\frac{144}{4}=36\text{cm} \end{gathered}$$

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