What is 9/21 plus 15/21? (Answer: 8/7)

Exact Answer

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Problem: What is 9/21 plus 15/21?
Formula / Expression: 9/21 + 15/21
Final Answer: 1 1/7 (8/7)
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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: 9/21 + 15/21

Step 2: Add the Numerators
Now add the numerators (9 + 15 = 24) and keep the common denominator 21 unchanged.
Working: 9 + 15/21 = 24/21

Step 3: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 24 and 21, which is 3. Divide both the numerator and denominator by 3.
Working: 24 ÷ 3/21 ÷ 3 = 8/7

Step 4: Convert Improper Fraction to a Mixed Number
Since the numerator (8) is greater than the denominator (7), divide 8 by 7: it goes in 1 whole time(s) with a remainder of 1, giving the mixed number 1 1/7.
Working: 8/7 = 1 1/7

Step 5: Decimal & Percentage Representation
Dividing the numerator 8 by denominator 7 produces a repeating decimal (approximately 1.142857, or 114.2857%).
Working: 8 ÷ 7 = 1.142857 (114.2857%)

Key Values:
- Simplified Fraction: 8/7
- Mixed Number Form: 1 1/7
- Decimal Value: 1.142857
- Percentage: 114.2857%

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Solved with FractionsCalc:
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9/21 + 15/21 = 8/7

Simplified Fraction

8/7

Mixed Number

1 1/7

Decimal Value

1.142857

Percentage

114.2857%

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Step-by-Step Solution: 9/21 + 15/21

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.

9/21 + 15/21

Step 2

Add the Numerators

Now add the numerators (9 + 15 = 24) and keep the common denominator 21 unchanged.

9 + 15/21 = 24/21

Step 3

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 24 and 21, which is 3. Divide both the numerator and denominator by 3.

24 ÷ 3/21 ÷ 3 = 8/7

Step 4

Convert Improper Fraction to a Mixed Number

Since the numerator (8) is greater than the denominator (7), divide 8 by 7: it goes in 1 whole time(s) with a remainder of 1, giving the mixed number 1 1/7.

8/7 = 11/7

Step 5

Decimal & Percentage Representation

Dividing the numerator 8 by denominator 7 produces a repeating decimal (approximately 1.142857, or 114.2857%).

8 ÷ 7 = 1.142857 (114.2857%)

Visual Representation

The diagram below illustrates 9/21 plus 15/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`8/7`
Mixed Number Form	`1 1/7`
Decimal Form	`1.142857`
Percentage	`114.2857%`

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Frequently Asked Questions

What is 9/21 plus 15/21 as a fraction?

9/21 + 15/21 in simplest fraction form is 8/7 (or 1 1/7 as a mixed number).

What is 9/21 plus 15/21 as a decimal?

9/21 + 15/21 converted to a decimal is 1.142857.

What is 9/21 plus 15/21 as a percentage?

9/21 + 15/21 expressed as a percentage is 114.2857%.

How do you write 9/21 plus 15/21 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 8/7 can be written as the mixed number 1 1/7.

Does 9/21 plus 15/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.142857...) because the denominator contains prime factors other than 2 and 5.