What is 5/21 plus 9/21?
5/21 plus 9/21 equals 2/3 (or 0.666667 in decimal form). Learn the step-by-step solution to add 5/21 and 9/21 using Least Common Denominator and simplification.
Exact Answer
5/21 + 9/21 = 2/3
Simplified Fraction
2/3
Mixed Number
Proper (2/3)
Decimal Value
0.666667
Percentage
66.6667%
Step-by-Step Solution: 5/21 + 9/21
Step 1
Check the Denominators (Like Fractions)
Both fractions already share the identical denominator (21). Because these are like fractions, no conversion to a common denominator is required—we directly add their numerators while keeping the denominator 21.
5/21 + 9/21
Step 2
Add the Numerators
Now add the numerators (5 + 9 = 14) and keep the common denominator 21 unchanged.
5 + 9/21 = 14/21
Step 3
Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 14 and 21, which is 7. Divide both the numerator and denominator by 7.
14 ÷ 7/21 ÷ 7 = 2/3
Step 4
Decimal & Percentage Representation
Dividing the numerator 2 by denominator 3 produces a repeating decimal (approximately 0.666667, or 66.6667%).
2 ÷ 3 = 0.666667 (66.6667%)
Visual Representation
The diagram below illustrates 5/21 plus 9/21 visually:
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Summary & Alternative Representations
| Property / Format | Value |
|---|---|
| Lowest Terms Fraction | 2/3 |
| Mixed Number Form | 2/3 |
| Decimal Form | 0.666667 |
| Percentage | 66.6667% |
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Frequently Asked Questions
What is 5/21 plus 9/21 as a fraction?
5/21 + 9/21 in simplest fraction form is 2/3.
What is 5/21 plus 9/21 as a decimal?
5/21 + 9/21 converted to a decimal is 0.666667.
What is 5/21 plus 9/21 as a percentage?
5/21 + 9/21 expressed as a percentage is 66.6667%.
Does 5/21 plus 9/21 result in a terminating or repeating decimal?
It results in a repeating decimal (approximately 0.666667...) because the denominator contains prime factors other than 2 and 5.