Parallelogram

Side a of a parallelogram is twice longer than side b. Its circumference is 78 dm. Calculate the length of the sides of a parallelogram.

Correct answer:

a =  26 dm
b =  13 dm

Step-by-step explanation:

$$\begin{gathered} a=2b \\ 2(a+b)=78 \\ 2(a+a/2)=78 \\ 2\cdot (a+a/2)=78 \\ 6a=156 \\ a=\frac{156}{6}=26 \\ a=26=26\text{dm} \end{gathered}$$

$b=a/2=26/2=13\text{dm}$

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