# The length of a rectangle is twice as large as its width, and its perimeter is 210 m. What are the length and width of the rectangle?

The perimeter of a rectangle is $2 l + 2 w$. Since we know $l = 2 w$ we can substitute that in: $2 \left(2 w\right) + 2 w = 4 w + 2 w = 6 w$.
So $6 w = 210$, then $w = \frac{210}{6} = 35$ $m$, and the length is twice that, $70$ $m$.