What is 6/18 plus 8/21? (Answer: 5/7)

Exact Answer

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Problem: What is 6/18 plus 8/21?
Formula / Expression: 6/18 + 8/21
Final Answer: 5/7
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 18 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 126 (which is smaller than their product 18 × 21 = 378, keeping the calculation simpler).
Working: LCD(18, 21) = 126

Step 2: Convert to Equivalent Fractions with Common Denominator 126
Multiply the numerator and denominator of 6/18 by 7, and multiply the numerator and denominator of 8/21 by 6 so both fractions share the common base 126.
Working: 6 × 7/18 × 7 = 42/126 and 8 × 6/21 × 6 = 48/126

Step 3: Add the Numerators
Now add the numerators (42 + 48 = 90) and keep the common denominator 126 unchanged.
Working: 42 + 48/126 = 90/126

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 90 and 126, which is 18. Divide both the numerator and denominator by 18.
Working: 90 ÷ 18/126 ÷ 18 = 5/7

Step 5: Decimal & Percentage Representation
Dividing the numerator 5 by denominator 7 produces a repeating decimal (approximately 0.714286, or 71.4286%).
Working: 5 ÷ 7 = 0.714286 (71.4286%)

Key Values:
- Simplified Fraction: 5/7
- Mixed Number Form: 5/7
- Decimal Value: 0.714286
- Percentage: 71.4286%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-6-18-plus-8-21/
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6/18 + 8/21 = 5/7

Simplified Fraction

5/7

Mixed Number

Proper (5/7)

Decimal Value

0.714286

Percentage

71.4286%

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Step-by-Step Solution: 6/18 + 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 18 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 126 (which is smaller than their product 18 × 21 = 378, keeping the calculation simpler).

LCD(18, 21) = 126

Step 2

Convert to Equivalent Fractions with Common Denominator 126

Multiply the numerator and denominator of 6/18 by 7, and multiply the numerator and denominator of 8/21 by 6 so both fractions share the common base 126.

6 × 7/18 × 7 = 42/126 and 8 × 6/21 × 6 = 48/126

Step 3

Add the Numerators

Now add the numerators (42 + 48 = 90) and keep the common denominator 126 unchanged.

42 + 48/126 = 90/126

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 90 and 126, which is 18. Divide both the numerator and denominator by 18.

90 ÷ 18/126 ÷ 18 = 5/7

Step 5

Decimal & Percentage Representation

Dividing the numerator 5 by denominator 7 produces a repeating decimal (approximately 0.714286, or 71.4286%).

5 ÷ 7 = 0.714286 (71.4286%)

Visual Representation

The diagram below illustrates 6/18 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`5/7`
Mixed Number Form	`5/7`
Decimal Form	`0.714286`
Percentage	`71.4286%`

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Frequently Asked Questions

What is 6/18 plus 8/21 as a fraction?

6/18 + 8/21 in simplest fraction form is 5/7.

What is 6/18 plus 8/21 as a decimal?

6/18 + 8/21 converted to a decimal is 0.714286.

What is 6/18 plus 8/21 as a percentage?

6/18 + 8/21 expressed as a percentage is 71.4286%.

Does 6/18 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.714286...) because the denominator contains prime factors other than 2 and 5.