Perimeter is the sum of all the dimension of the sides of a shape Perimeter of the shape =25cm+24cm+ half the circumference of the circular portion Circumference =2πr Where r= radius. Diameter =2x radius Circumference =πx diameter Length of the circular portion =
Circumference
2
Length of the circular portion =
πx diameter
2
Perimeter of the shape =25cm+24cm+
πx diameter
2
But perimeter =71 71cm=25cm+24cm+
πx diameter
2
71=49+
πx diameter
2
71−49=
πx diameter
2
22=
πx diameter
2
Multiply both sides of the equation by 2 to get rid of the denominator 2 . 22×2=π× diameter But π=
22
7
22×2=
22
7
× diameter Get rid of the fraction by multiplying both sides of the equation by the denominator 7 22×2×7=22× diameter Divide both sides by 22 to make diameter the subject Diameter =