Question

The circumference of a circular clock is 31.4 inches.What is the diameter of the clock

Answer 1

Circumference of a circle=πd
d=diameter
Circumference=31.4 in
π=3.141592654...

31.4 in=πd
d=3.14 in / π=0.999493...in≈1 in

Answer: diameter=1 in

Answer 2

The circumference formula is 
C = $2 \pi$r

We know the circumference, so lets find the radius and we will get the diameter.

31.4 = 2$\pi r$
divide by 2$\pi$ to isolate r

$\frac{31.4}{2 \pi }$ = $\frac{2 \pi r}{2 \pi }$
2$\pi$ and 2$\pi$ cancels out.

0.4997 = r
0.5 in ≈ r        (approximately)

Diameter is 2 × radius
                   2 × 0.5
                   1 in