Answers

Add 21/72 and 80/90

21/72 + 80/90 is 85/72.

Steps for adding fractions

1. Find the least common denominator or LCM of the two denominators:
   LCM of 72 and 90 is 360
   
   Next, find the equivalent fraction of both fractional numbers with denominator 360
2. For the 1st fraction, since 72 × 5 = 360,
   21/72 = 21 × 5/72 × 5 = 105/360
3. Likewise, for the 2nd fraction, since 90 × 4 = 360,
   80/90 = 80 × 4/90 × 4 = 320/360
4. Add the two like fractions:
   105/360 + 320/360 = 105 + 320/360 = 425/360
5. 425/360 simplified gives 85/72
6. So, 21/72 + 80/90 = 85/72
   In mixed form: 113/72

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