What is 6/15 plus 12/21? (Answer: 34/35)

Exact Answer

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Problem: What is 6/15 plus 12/21?
Formula / Expression: 6/15 + 12/21
Final Answer: 34/35
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 15 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 105 (which is smaller than their product 15 × 21 = 315, keeping the calculation simpler).
Working: LCD(15, 21) = 105

Step 2: Convert to Equivalent Fractions with Common Denominator 105
Multiply the numerator and denominator of 6/15 by 7, and multiply the numerator and denominator of 12/21 by 5 so both fractions share the common base 105.
Working: 6 × 7/15 × 7 = 42/105 and 12 × 5/21 × 5 = 60/105

Step 3: Add the Numerators
Now add the numerators (42 + 60 = 102) and keep the common denominator 105 unchanged.
Working: 42 + 60/105 = 102/105

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 102 and 105, which is 3. Divide both the numerator and denominator by 3.
Working: 102 ÷ 3/105 ÷ 3 = 34/35

Step 5: Decimal & Percentage Representation
Dividing the numerator 34 by denominator 35 produces a repeating decimal (approximately 0.971429, or 97.1429%).
Working: 34 ÷ 35 = 0.971429 (97.1429%)

Key Values:
- Simplified Fraction: 34/35
- Mixed Number Form: 34/35
- Decimal Value: 0.971429
- Percentage: 97.1429%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-6-15-plus-12-21/
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6/15 + 12/21 = 34/35

Simplified Fraction

34/35

Mixed Number

Proper (34/35)

Decimal Value

0.971429

Percentage

97.1429%

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Step-by-Step Solution: 6/15 + 12/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 15 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 105 (which is smaller than their product 15 × 21 = 315, keeping the calculation simpler).

LCD(15, 21) = 105

Step 2

Convert to Equivalent Fractions with Common Denominator 105

Multiply the numerator and denominator of 6/15 by 7, and multiply the numerator and denominator of 12/21 by 5 so both fractions share the common base 105.

6 × 7/15 × 7 = 42/105 and 12 × 5/21 × 5 = 60/105

Step 3

Add the Numerators

Now add the numerators (42 + 60 = 102) and keep the common denominator 105 unchanged.

42 + 60/105 = 102/105

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 102 and 105, which is 3. Divide both the numerator and denominator by 3.

102 ÷ 3/105 ÷ 3 = 34/35

Step 5

Decimal & Percentage Representation

Dividing the numerator 34 by denominator 35 produces a repeating decimal (approximately 0.971429, or 97.1429%).

34 ÷ 35 = 0.971429 (97.1429%)

Visual Representation

The diagram below illustrates 6/15 plus 12/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`34/35`
Mixed Number Form	`34/35`
Decimal Form	`0.971429`
Percentage	`97.1429%`

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Frequently Asked Questions

What is 6/15 plus 12/21 as a fraction?

6/15 + 12/21 in simplest fraction form is 34/35.

What is 6/15 plus 12/21 as a decimal?

6/15 + 12/21 converted to a decimal is 0.971429.

What is 6/15 plus 12/21 as a percentage?

6/15 + 12/21 expressed as a percentage is 97.1429%.

Does 6/15 plus 12/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.971429...) because the denominator contains prime factors other than 2 and 5.