When a fraction is reduced to lowest terms, the only factor the numerator and denominator have in common is . 10
1
0
5

This means that there is no number, except 1, that can be divided evenly into both the numerator and the denominator. To reduce a fraction to lowest terms, divide the numerator and denominator by their Greatest Common Factor (GCF). This is also called simplifying the fraction.

D = 10 cm,  r = 5 cm;
A = 4 r² π = 4 · 5² · 3.14 = 314 cm²
In one minute:
A 1 = 314 - 7 = 307 cm²
307 = 4 r 1² π
r 1² = 307: 12.56
r 1² = 24.44
r 1 = 4.944
d 1 = 2 · 4.944 = 9.888 cm
10 - 9.888 = 0.112

The rate at which the diameter decreases is 0.112 cm / min.