Question

Rectangle L has a perimeter of 108 centimetres. Opposite sites of the rectangle have lengths of 27 cm each. what is its missing side lenghts?

Answer 1

The perimeter P of a rectangle of length L and width l is
$P = 2L + 2l$
Here you know P =108 and l=27. Thus you have the equation
$108 = 2L + 2 \times 27 = 2L + 54$
You simplify a bit by moving the 54 on the left side
$54 = 2L$
and you find L=27 cm.

Oh my, this is a square!