Two opposite sides of a square are increased by 5 cm to form a rectangle. if the rectangle has a perimeter of 70 cm's, what was the length of a side of the original square?

This could be done in two different ways. One is by first knowing the perimeter of rectangle, which in this case is 70, then identifying the increase of the opposite side, increased by 5 which is equal to 10 overall. After that let us establish a working equation, square = rectangle - 10. By that let us substitute the value, square = 70 - 10; square = 60 cm. Then remember that square has four equal side, so square = 60 divided by 4 = 15. So the original side of square is 15 cm.

Let the side of square being an x 
to creat the rectangle this length of sides of square was increased by 5 cm 

so the rectangle has perimeter 70 cm 

in this way we can writing 

2x +2(x+5) = 70 

2x +2x +10 = 70

4x = 60

x = 15

so the length of a side of the original squae was 15 cm