Question

the width of a rectangle is fixed at 18 cm what lengths will make the perimeter greater than 78 cm
length must be greater than cm

Answer 1

the perimeter has to be greater than 78
perimeter of rectangle is (2 x width) + (2 x length)
the perimeter must be greater than 78, so
(2 x width) + (2 x length) > 78
(2 x 18) + (2 x length) >78
36 + (2 x lenght) > 78
2 x length > 78-36
length> 42/2
length> 21
the length must be greater than 21cm

Answer 2

2l>78-36
l>21