Subtract 1/40 from 21/42
21/42 - 1/40 is 19/40.
Steps for subtracting fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 40 is 840
Next, find the equivalent fraction of both fractional numbers with denominator 840 - For the 1st fraction, since 42 × 20 = 840,
21/42 = 21 × 20/42 × 20 = 420/840 - Likewise, for the 2nd fraction, since 40 × 21 = 840,
1/40 = 1 × 21/40 × 21 = 21/840 - Subtract the two like fractions:
420/840 - 21/840 = 420 - 21/840 = 399/840 - After reducing the fraction, the answer is 19/40
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42-2/40 21/84-1/40 21/42-1/80 63/42-1/40 21/42-3/40 21/42-5/40 21/42-7/40