Subtract 15/80 from 21/4, Solve 5 1/4

Subtract 15/80 from 21/4

1^st number: 5 1/4, 2^nd number: 15/80

21/4 - 15/80 is 81/16.

Find the least common denominator or LCM of the two denominators:
LCM of 4 and 80 is 80

Next, find the equivalent fraction of both fractional numbers with denominator 80
For the 1st fraction, since 4 × 20 = 80,
21/4 = 21 × 20/4 × 20 = 420/80
Likewise, for the 2nd fraction, since 80 × 1 = 80,
15/80 = 15 × 1/80 × 1 = 15/80
Subtract the two like fractions:
420/80 - 15/80 = 420 - 15/80 = 405/80
After reducing the fraction, the answer is 81/16
In mixed form: 51/16

MathStep (Works offline)

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