What is 3/31 plus 9/13? (Answer: 318/403)

Exact Answer

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Problem: What is 3/31 plus 9/13?
Formula / Expression: 3/31 + 9/13
Final Answer: 318/403
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 31 and 13 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 31 × 13 = 403.
Working: LCD(31, 13) = 403

Step 2: Convert to Equivalent Fractions with Common Denominator 403
Multiply the numerator and denominator of 3/31 by 13, and multiply the numerator and denominator of 9/13 by 31 so both fractions share the common base 403.
Working: 3 × 13/31 × 13 = 39/403 and 9 × 31/13 × 31 = 279/403

Step 3: Add the Numerators
Now add the numerators (39 + 279 = 318) and keep the common denominator 403 unchanged.
Working: 39 + 279/403 = 318/403

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 318 and 403 is 1, confirming that 318/403 cannot be reduced further—it is already in its simplest irreducible form.
Working: 318/403

Step 5: Decimal & Percentage Representation
Dividing the numerator 318 by denominator 403 produces a repeating decimal (approximately 0.789082, or 78.9082%).
Working: 318 ÷ 403 = 0.789082 (78.9082%)

Key Values:
- Simplified Fraction: 318/403
- Mixed Number Form: 318/403
- Decimal Value: 0.789082
- Percentage: 78.9082%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-3-31-plus-9-13/
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3/31 + 9/13 = 318/403

Simplified Fraction

318/403

Mixed Number

Proper (318/403)

Decimal Value

0.789082

Percentage

78.9082%

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Step-by-Step Solution: 3/31 + 9/13

Step 1

Find the Least Common Denominator (LCD)

The denominators 31 and 13 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 31 × 13 = 403.

LCD(31, 13) = 403

Step 2

Convert to Equivalent Fractions with Common Denominator 403

Multiply the numerator and denominator of 3/31 by 13, and multiply the numerator and denominator of 9/13 by 31 so both fractions share the common base 403.

3 × 13/31 × 13 = 39/403 and 9 × 31/13 × 31 = 279/403

Step 3

Add the Numerators

Now add the numerators (39 + 279 = 318) and keep the common denominator 403 unchanged.

39 + 279/403 = 318/403

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 318 and 403 is 1, confirming that 318/403 cannot be reduced further—it is already in its simplest irreducible form.

318/403

Step 5

Decimal & Percentage Representation

Dividing the numerator 318 by denominator 403 produces a repeating decimal (approximately 0.789082, or 78.9082%).

318 ÷ 403 = 0.789082 (78.9082%)

Visual Representation

The diagram below illustrates 3/31 plus 9/13 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`318/403`
Mixed Number Form	`318/403`
Decimal Form	`0.789082`
Percentage	`78.9082%`

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Frequently Asked Questions

What is 3/31 plus 9/13 as a fraction?

3/31 + 9/13 in simplest fraction form is 318/403.

What is 3/31 plus 9/13 as a decimal?

3/31 + 9/13 converted to a decimal is 0.789082.

What is 3/31 plus 9/13 as a percentage?

3/31 + 9/13 expressed as a percentage is 78.9082%.

Does 3/31 plus 9/13 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.789082...) because the denominator contains prime factors other than 2 and 5.