Add 81/84 and 70/40, Solve 81/84 + 1 30/40 as a fraction

Add 81/84 and 70/40

1^st number: 81/84, 2^nd number: 1 30/40

81/84 + 70/40 is 19/7.

Find the least common denominator or LCM of the two denominators:
LCM of 84 and 40 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 84 × 10 = 840,
81/84 = 81 × 10/84 × 10 = 810/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
70/40 = 70 × 21/40 × 21 = 1470/840
Add the two like fractions:
810/840 + 1470/840 = 810 + 1470/840 = 2280/840
2280/840 simplified gives 19/7
So, 81/84 + 70/40 = 19/7
In mixed form: 25/7

MathStep (Works offline)

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