What is 15/51 plus 8/21? (Answer: 241/357)

Exact Answer

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Problem: What is 15/51 plus 8/21?
Formula / Expression: 15/51 + 8/21
Final Answer: 241/357
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 51 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 357 (which is smaller than their product 51 × 21 = 1071, keeping the calculation simpler).
Working: LCD(51, 21) = 357

Step 2: Convert to Equivalent Fractions with Common Denominator 357
Multiply the numerator and denominator of 15/51 by 7, and multiply the numerator and denominator of 8/21 by 17 so both fractions share the common base 357.
Working: 15 × 7/51 × 7 = 105/357 and 8 × 17/21 × 17 = 136/357

Step 3: Add the Numerators
Now add the numerators (105 + 136 = 241) and keep the common denominator 357 unchanged.
Working: 105 + 136/357 = 241/357

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 241 and 357 is 1, confirming that 241/357 cannot be reduced further—it is already in its simplest irreducible form.
Working: 241/357

Step 5: Decimal & Percentage Representation
Dividing the numerator 241 by denominator 357 produces a repeating decimal (approximately 0.67507, or 67.507%).
Working: 241 ÷ 357 = 0.67507 (67.507%)

Key Values:
- Simplified Fraction: 241/357
- Mixed Number Form: 241/357
- Decimal Value: 0.67507
- Percentage: 67.507%

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Solved with FractionsCalc:
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15/51 + 8/21 = 241/357

Simplified Fraction

241/357

Mixed Number

Proper (241/357)

Decimal Value

0.67507

Percentage

67.507%

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Step-by-Step Solution: 15/51 + 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 51 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 357 (which is smaller than their product 51 × 21 = 1071, keeping the calculation simpler).

LCD(51, 21) = 357

Step 2

Convert to Equivalent Fractions with Common Denominator 357

Multiply the numerator and denominator of 15/51 by 7, and multiply the numerator and denominator of 8/21 by 17 so both fractions share the common base 357.

15 × 7/51 × 7 = 105/357 and 8 × 17/21 × 17 = 136/357

Step 3

Add the Numerators

Now add the numerators (105 + 136 = 241) and keep the common denominator 357 unchanged.

105 + 136/357 = 241/357

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 241 and 357 is 1, confirming that 241/357 cannot be reduced further—it is already in its simplest irreducible form.

241/357

Step 5

Decimal & Percentage Representation

Dividing the numerator 241 by denominator 357 produces a repeating decimal (approximately 0.67507, or 67.507%).

241 ÷ 357 = 0.67507 (67.507%)

Visual Representation

The diagram below illustrates 15/51 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`241/357`
Mixed Number Form	`241/357`
Decimal Form	`0.67507`
Percentage	`67.507%`

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Frequently Asked Questions

What is 15/51 plus 8/21 as a fraction?

15/51 + 8/21 in simplest fraction form is 241/357.

What is 15/51 plus 8/21 as a decimal?

15/51 + 8/21 converted to a decimal is 0.67507.

What is 15/51 plus 8/21 as a percentage?

15/51 + 8/21 expressed as a percentage is 67.507%.

Does 15/51 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.67507...) because the denominator contains prime factors other than 2 and 5.