What is 15/43 plus 8/21? (Answer: 659/903)

Exact Answer

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Problem: What is 15/43 plus 8/21?
Formula / Expression: 15/43 + 8/21
Final Answer: 659/903
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 43 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 43 × 21 = 903.
Working: LCD(43, 21) = 903

Step 2: Convert to Equivalent Fractions with Common Denominator 903
Multiply the numerator and denominator of 15/43 by 21, and multiply the numerator and denominator of 8/21 by 43 so both fractions share the common base 903.
Working: 15 × 21/43 × 21 = 315/903 and 8 × 43/21 × 43 = 344/903

Step 3: Add the Numerators
Now add the numerators (315 + 344 = 659) and keep the common denominator 903 unchanged.
Working: 315 + 344/903 = 659/903

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 659 and 903 is 1, confirming that 659/903 cannot be reduced further—it is already in its simplest irreducible form.
Working: 659/903

Step 5: Decimal & Percentage Representation
Dividing the numerator 659 by denominator 903 produces a repeating decimal (approximately 0.72979, or 72.979%).
Working: 659 ÷ 903 = 0.72979 (72.979%)

Key Values:
- Simplified Fraction: 659/903
- Mixed Number Form: 659/903
- Decimal Value: 0.72979
- Percentage: 72.979%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-15-43-plus-8-21/
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15/43 + 8/21 = 659/903

Simplified Fraction

659/903

Mixed Number

Proper (659/903)

Decimal Value

0.72979

Percentage

72.979%

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Step-by-Step Solution: 15/43 + 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 43 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 43 × 21 = 903.

LCD(43, 21) = 903

Step 2

Convert to Equivalent Fractions with Common Denominator 903

Multiply the numerator and denominator of 15/43 by 21, and multiply the numerator and denominator of 8/21 by 43 so both fractions share the common base 903.

15 × 21/43 × 21 = 315/903 and 8 × 43/21 × 43 = 344/903

Step 3

Add the Numerators

Now add the numerators (315 + 344 = 659) and keep the common denominator 903 unchanged.

315 + 344/903 = 659/903

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 659 and 903 is 1, confirming that 659/903 cannot be reduced further—it is already in its simplest irreducible form.

659/903

Step 5

Decimal & Percentage Representation

Dividing the numerator 659 by denominator 903 produces a repeating decimal (approximately 0.72979, or 72.979%).

659 ÷ 903 = 0.72979 (72.979%)

Visual Representation

The diagram below illustrates 15/43 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`659/903`
Mixed Number Form	`659/903`
Decimal Form	`0.72979`
Percentage	`72.979%`

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Frequently Asked Questions

What is 15/43 plus 8/21 as a fraction?

15/43 + 8/21 in simplest fraction form is 659/903.

What is 15/43 plus 8/21 as a decimal?

15/43 + 8/21 converted to a decimal is 0.72979.

What is 15/43 plus 8/21 as a percentage?

15/43 + 8/21 expressed as a percentage is 72.979%.

Does 15/43 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.72979...) because the denominator contains prime factors other than 2 and 5.