The formula of circumference: 2兀r
Take 3.14 as 兀
Circumference of circle with radius 4.2 units
=4.2x2x3.14
=26.376units
Circumference of circle with diameter 7.4
=7.4x3.14
=23.236 units
Circumference of circle with diameter 11 units
=11x3.14
=34.54 units
Circumference of circle with radius 9.5 units
=9.5x3.14
=29.83 units
Hope it helps!
