Subtract 9/40 from 15/21, Solve 15/21

Subtract 9/40 from 15/21

15/21 - 9/40 is 137/280.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 40 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 21 × 40 = 840,
15/21 = 15 × 40/21 × 40 = 600/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
9/40 = 9 × 21/40 × 21 = 189/840
Subtract the two like fractions:
600/840 - 189/840 = 600 - 189/840 = 411/840
After reducing the fraction, the answer is 137/280

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