One method to convert 21/42 to a decimal is by using the division method. Before we move ahead to the method, here is a quick recap on fractions: A fraction is a number representation that is broken down into two parts - the number on top is called the numerator, and the number on the bottom is called the denominator. To get a decimal using the division method, simply divide the numerator 21 by the denominator 42:
21 (numerator) ÷ 42 (denominator) = 0.5
And there you go! We got 0.5 as the answer when you convert 21/42 to a decimal.