What is 5/17 plus 9/21? (Answer: 86/119)

Exact Answer

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Problem: What is 5/17 plus 9/21?
Formula / Expression: 5/17 + 9/21
Final Answer: 86/119
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 17 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 17 × 21 = 357.
Working: LCD(17, 21) = 357

Step 2: Convert to Equivalent Fractions with Common Denominator 357
Multiply the numerator and denominator of 5/17 by 21, and multiply the numerator and denominator of 9/21 by 17 so both fractions share the common base 357.
Working: 5 × 21/17 × 21 = 105/357 and 9 × 17/21 × 17 = 153/357

Step 3: Add the Numerators
Now add the numerators (105 + 153 = 258) and keep the common denominator 357 unchanged.
Working: 105 + 153/357 = 258/357

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 258 and 357, which is 3. Divide both the numerator and denominator by 3.
Working: 258 ÷ 3/357 ÷ 3 = 86/119

Step 5: Decimal & Percentage Representation
Dividing the numerator 86 by denominator 119 produces a repeating decimal (approximately 0.722689, or 72.2689%).
Working: 86 ÷ 119 = 0.722689 (72.2689%)

Key Values:
- Simplified Fraction: 86/119
- Mixed Number Form: 86/119
- Decimal Value: 0.722689
- Percentage: 72.2689%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-5-17-plus-9-21/
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5/17 + 9/21 = 86/119

Simplified Fraction

86/119

Mixed Number

Proper (86/119)

Decimal Value

0.722689

Percentage

72.2689%

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Step-by-Step Solution: 5/17 + 9/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 17 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 17 × 21 = 357.

LCD(17, 21) = 357

Step 2

Convert to Equivalent Fractions with Common Denominator 357

Multiply the numerator and denominator of 5/17 by 21, and multiply the numerator and denominator of 9/21 by 17 so both fractions share the common base 357.

5 × 21/17 × 21 = 105/357 and 9 × 17/21 × 17 = 153/357

Step 3

Add the Numerators

Now add the numerators (105 + 153 = 258) and keep the common denominator 357 unchanged.

105 + 153/357 = 258/357

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 258 and 357, which is 3. Divide both the numerator and denominator by 3.

258 ÷ 3/357 ÷ 3 = 86/119

Step 5

Decimal & Percentage Representation

Dividing the numerator 86 by denominator 119 produces a repeating decimal (approximately 0.722689, or 72.2689%).

86 ÷ 119 = 0.722689 (72.2689%)

Visual Representation

The diagram below illustrates 5/17 plus 9/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`86/119`
Mixed Number Form	`86/119`
Decimal Form	`0.722689`
Percentage	`72.2689%`

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Frequently Asked Questions

What is 5/17 plus 9/21 as a fraction?

5/17 + 9/21 in simplest fraction form is 86/119.

What is 5/17 plus 9/21 as a decimal?

5/17 + 9/21 converted to a decimal is 0.722689.

What is 5/17 plus 9/21 as a percentage?

5/17 + 9/21 expressed as a percentage is 72.2689%.

Does 5/17 plus 9/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.722689...) because the denominator contains prime factors other than 2 and 5.