Add 42/2 and 21/84, Solve 21 0/2 + 21/84 as a fraction

Add 42/2 and 21/84

1^st number: 21 0/2, 2^nd number: 21/84

42/2 + 21/84 is 85/4.

Find the least common denominator or LCM of the two denominators:
LCM of 2 and 84 is 84

Next, find the equivalent fraction of both fractional numbers with denominator 84
For the 1st fraction, since 2 × 42 = 84,
42/2 = 42 × 42/2 × 42 = 1764/84
Likewise, for the 2nd fraction, since 84 × 1 = 84,
21/84 = 21 × 1/84 × 1 = 21/84
Add the two like fractions:
1764/84 + 21/84 = 1764 + 21/84 = 1785/84
1785/84 simplified gives 85/4
So, 42/2 + 21/84 = 85/4
In mixed form: 211/4

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad