Add 21/42 and 90/8, Solve 21/42 + 11 2/8 as a fraction

Add 21/42 and 90/8

1^st number: 21/42, 2^nd number: 11 2/8

21/42 + 90/8 is 47/4.

Find the least common denominator or LCM of the two denominators:
LCM of 42 and 8 is 168

Next, find the equivalent fraction of both fractional numbers with denominator 168
For the 1st fraction, since 42 × 4 = 168,
21/42 = 21 × 4/42 × 4 = 84/168
Likewise, for the 2nd fraction, since 8 × 21 = 168,
90/8 = 90 × 21/8 × 21 = 1890/168
Add the two like fractions:
84/168 + 1890/168 = 84 + 1890/168 = 1974/168
1974/168 simplified gives 47/4
So, 21/42 + 90/8 = 47/4
In mixed form: 113/4

MathStep (Works offline)

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