What is 5/21 plus 12/21? (Answer: 17/21)

Exact Answer

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Problem: What is 5/21 plus 12/21?
Formula / Expression: 5/21 + 12/21
Final Answer: 17/21
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Step-by-Step Solution:

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.
Working: 5/21 + 12/21

Step 2: Add the Numerators
Now add the numerators (5 + 12 = 17) and keep the common denominator 21 unchanged.
Working: 5 + 12/21 = 17/21

Step 3: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 17 and 21 is 1, confirming that 17/21 cannot be reduced further—it is already in its simplest irreducible form.
Working: 17/21

Step 4: Decimal & Percentage Representation
Dividing the numerator 17 by denominator 21 produces a repeating decimal (approximately 0.809524, or 80.9524%).
Working: 17 ÷ 21 = 0.809524 (80.9524%)

Key Values:
- Simplified Fraction: 17/21
- Mixed Number Form: 17/21
- Decimal Value: 0.809524
- Percentage: 80.9524%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-5-21-plus-12-21/
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5/21 + 12/21 = 17/21

Simplified Fraction

17/21

Mixed Number

Proper (17/21)

Decimal Value

0.809524

Percentage

80.9524%

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Step-by-Step Solution: 5/21 + 12/21

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 + 12/21

Step 2

Add the Numerators

Now add the numerators (5 + 12 = 17) and keep the common denominator 21 unchanged.

5 + 12/21 = 17/21

Step 3

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 17 and 21 is 1, confirming that 17/21 cannot be reduced further—it is already in its simplest irreducible form.

17/21

Step 4

Decimal & Percentage Representation

Dividing the numerator 17 by denominator 21 produces a repeating decimal (approximately 0.809524, or 80.9524%).

17 ÷ 21 = 0.809524 (80.9524%)

Visual Representation

The diagram below illustrates 5/21 plus 12/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`17/21`
Mixed Number Form	`17/21`
Decimal Form	`0.809524`
Percentage	`80.9524%`

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Frequently Asked Questions

What is 5/21 plus 12/21 as a fraction?

5/21 + 12/21 in simplest fraction form is 17/21.

What is 5/21 plus 12/21 as a decimal?

5/21 + 12/21 converted to a decimal is 0.809524.

What is 5/21 plus 12/21 as a percentage?

5/21 + 12/21 expressed as a percentage is 80.9524%.

Does 5/21 plus 12/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.809524...) because the denominator contains prime factors other than 2 and 5.