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

Subtract 21/40 from 9/21

9/21 - 21/40 is -27/280.

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,
9/21 = 9 × 40/21 × 40 = 360/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
21/40 = 21 × 21/40 × 21 = 441/840
Subtract the two like fractions:
360/840 - 441/840 = 360 - 441/840 = -81/840
After reducing the fraction, the answer is -27/280

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