What is 18/58 plus 8/21? (Answer: 421/609)

Exact Answer

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Problem: What is 18/58 plus 8/21?
Formula / Expression: 18/58 + 8/21
Final Answer: 421/609
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 58 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 58 × 21 = 1218.
Working: LCD(58, 21) = 1218

Step 2: Convert to Equivalent Fractions with Common Denominator 1218
Multiply the numerator and denominator of 18/58 by 21, and multiply the numerator and denominator of 8/21 by 58 so both fractions share the common base 1218.
Working: 18 × 21/58 × 21 = 378/1218 and 8 × 58/21 × 58 = 464/1218

Step 3: Add the Numerators
Now add the numerators (378 + 464 = 842) and keep the common denominator 1218 unchanged.
Working: 378 + 464/1218 = 842/1218

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 842 and 1218, which is 2. Divide both the numerator and denominator by 2.
Working: 842 ÷ 2/1218 ÷ 2 = 421/609

Step 5: Decimal & Percentage Representation
Dividing the numerator 421 by denominator 609 produces a repeating decimal (approximately 0.691297, or 69.1297%).
Working: 421 ÷ 609 = 0.691297 (69.1297%)

Key Values:
- Simplified Fraction: 421/609
- Mixed Number Form: 421/609
- Decimal Value: 0.691297
- Percentage: 69.1297%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-18-58-plus-8-21/
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18/58 + 8/21 = 421/609

Simplified Fraction

421/609

Mixed Number

Proper (421/609)

Decimal Value

0.691297

Percentage

69.1297%

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Step-by-Step Solution: 18/58 + 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 58 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 58 × 21 = 1218.

LCD(58, 21) = 1218

Step 2

Convert to Equivalent Fractions with Common Denominator 1218

Multiply the numerator and denominator of 18/58 by 21, and multiply the numerator and denominator of 8/21 by 58 so both fractions share the common base 1218.

18 × 21/58 × 21 = 378/1218 and 8 × 58/21 × 58 = 464/1218

Step 3

Add the Numerators

Now add the numerators (378 + 464 = 842) and keep the common denominator 1218 unchanged.

378 + 464/1218 = 842/1218

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 842 and 1218, which is 2. Divide both the numerator and denominator by 2.

842 ÷ 2/1218 ÷ 2 = 421/609

Step 5

Decimal & Percentage Representation

Dividing the numerator 421 by denominator 609 produces a repeating decimal (approximately 0.691297, or 69.1297%).

421 ÷ 609 = 0.691297 (69.1297%)

Visual Representation

The diagram below illustrates 18/58 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`421/609`
Mixed Number Form	`421/609`
Decimal Form	`0.691297`
Percentage	`69.1297%`

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Frequently Asked Questions

What is 18/58 plus 8/21 as a fraction?

18/58 + 8/21 in simplest fraction form is 421/609.

What is 18/58 plus 8/21 as a decimal?

18/58 + 8/21 converted to a decimal is 0.691297.

What is 18/58 plus 8/21 as a percentage?

18/58 + 8/21 expressed as a percentage is 69.1297%.

Does 18/58 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.691297...) because the denominator contains prime factors other than 2 and 5.