Question

find the diameter of the circle whose circumference is 15.7 cm

Answer 1

Circumference of circle=2πr=πd
15.7=πd
15.7=3.14d
15.7÷3.14=d
5=d
The diameter of the circle is 5cm.

Answer 2

given , 
circumference of the circle = 15.7 cm
therefore , 
circumference = 2πr
15.7 = 2 * 22/7 * r
15.7 = 44/7 * r
15.7 * 7/44 = r
2.49 = r
therefore radius of the circle = 2.49 cm and
diameter of the circle = 2.49 * 2 = 4.98 cm
 therefore the answer is 4.98 cm .
        i hope it helps..........................^_^