What is 12/51 plus 5/21? (Answer: 169/357)

Exact Answer

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Problem: What is 12/51 plus 5/21?
Formula / Expression: 12/51 + 5/21
Final Answer: 169/357
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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 12/51 by 7, and multiply the numerator and denominator of 5/21 by 17 so both fractions share the common base 357.
Working: 12 × 7/51 × 7 = 84/357 and 5 × 17/21 × 17 = 85/357

Step 3: Add the Numerators
Now add the numerators (84 + 85 = 169) and keep the common denominator 357 unchanged.
Working: 84 + 85/357 = 169/357

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 169 and 357 is 1, confirming that 169/357 cannot be reduced further—it is already in its simplest irreducible form.
Working: 169/357

Step 5: Decimal & Percentage Representation
Dividing the numerator 169 by denominator 357 produces a repeating decimal (approximately 0.473389, or 47.3389%).
Working: 169 ÷ 357 = 0.473389 (47.3389%)

Key Values:
- Simplified Fraction: 169/357
- Mixed Number Form: 169/357
- Decimal Value: 0.473389
- Percentage: 47.3389%

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Solved with FractionsCalc:
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12/51 + 5/21 = 169/357

Simplified Fraction

169/357

Mixed Number

Proper (169/357)

Decimal Value

0.473389

Percentage

47.3389%

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Step-by-Step Solution: 12/51 + 5/21

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 12/51 by 7, and multiply the numerator and denominator of 5/21 by 17 so both fractions share the common base 357.

12 × 7/51 × 7 = 84/357 and 5 × 17/21 × 17 = 85/357

Step 3

Add the Numerators

Now add the numerators (84 + 85 = 169) and keep the common denominator 357 unchanged.

84 + 85/357 = 169/357

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 169 and 357 is 1, confirming that 169/357 cannot be reduced further—it is already in its simplest irreducible form.

169/357

Step 5

Decimal & Percentage Representation

Dividing the numerator 169 by denominator 357 produces a repeating decimal (approximately 0.473389, or 47.3389%).

169 ÷ 357 = 0.473389 (47.3389%)

Visual Representation

The diagram below illustrates 12/51 plus 5/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`169/357`
Mixed Number Form	`169/357`
Decimal Form	`0.473389`
Percentage	`47.3389%`

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Frequently Asked Questions

What is 12/51 plus 5/21 as a fraction?

12/51 + 5/21 in simplest fraction form is 169/357.

What is 12/51 plus 5/21 as a decimal?

12/51 + 5/21 converted to a decimal is 0.473389.

What is 12/51 plus 5/21 as a percentage?

12/51 + 5/21 expressed as a percentage is 47.3389%.

Does 12/51 plus 5/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.473389...) because the denominator contains prime factors other than 2 and 5.