What is 4/21 plus 8/21?
4/21 plus 8/21 equals 4/7 (or 0.571429 in decimal form). Learn the step-by-step solution to add 4/21 and 8/21 using Least Common Denominator and simplification.
Exact Answer
4/21 + 8/21 = 4/7
Simplified Fraction
4/7
Mixed Number
Proper (4/7)
Decimal Value
0.571429
Percentage
57.1429%
Step-by-Step Solution: 4/21 + 8/21
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.
4/21 + 8/21
Step 2
Add the Numerators
Now add the numerators (4 + 8 = 12) and keep the common denominator 21 unchanged.
4 + 8/21 = 12/21
Step 3
Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 12 and 21, which is 3. Divide both the numerator and denominator by 3.
12 ÷ 3/21 ÷ 3 = 4/7
Step 4
Decimal & Percentage Representation
Dividing the numerator 4 by denominator 7 produces a repeating decimal (approximately 0.571429, or 57.1429%).
4 ÷ 7 = 0.571429 (57.1429%)
Visual Representation
The diagram below illustrates 4/21 plus 8/21 visually:
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Summary & Alternative Representations
| Property / Format | Value |
|---|---|
| Lowest Terms Fraction | 4/7 |
| Mixed Number Form | 4/7 |
| Decimal Form | 0.571429 |
| Percentage | 57.1429% |
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Frequently Asked Questions
What is 4/21 plus 8/21 as a fraction?
4/21 + 8/21 in simplest fraction form is 4/7.
What is 4/21 plus 8/21 as a decimal?
4/21 + 8/21 converted to a decimal is 0.571429.
What is 4/21 plus 8/21 as a percentage?
4/21 + 8/21 expressed as a percentage is 57.1429%.
Does 4/21 plus 8/21 result in a terminating or repeating decimal?
It results in a repeating decimal (approximately 0.571429...) because the denominator contains prime factors other than 2 and 5.