What is 15/39 plus 11/21? (Answer: 248/273)

Exact Answer

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Problem: What is 15/39 plus 11/21?
Formula / Expression: 15/39 + 11/21
Final Answer: 248/273
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 39 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 273 (which is smaller than their product 39 × 21 = 819, keeping the calculation simpler).
Working: LCD(39, 21) = 273

Step 2: Convert to Equivalent Fractions with Common Denominator 273
Multiply the numerator and denominator of 15/39 by 7, and multiply the numerator and denominator of 11/21 by 13 so both fractions share the common base 273.
Working: 15 × 7/39 × 7 = 105/273 and 11 × 13/21 × 13 = 143/273

Step 3: Add the Numerators
Now add the numerators (105 + 143 = 248) and keep the common denominator 273 unchanged.
Working: 105 + 143/273 = 248/273

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 248 and 273 is 1, confirming that 248/273 cannot be reduced further—it is already in its simplest irreducible form.
Working: 248/273

Step 5: Decimal & Percentage Representation
Dividing the numerator 248 by denominator 273 produces a repeating decimal (approximately 0.908425, or 90.8425%).
Working: 248 ÷ 273 = 0.908425 (90.8425%)

Key Values:
- Simplified Fraction: 248/273
- Mixed Number Form: 248/273
- Decimal Value: 0.908425
- Percentage: 90.8425%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-15-39-plus-11-21/
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15/39 + 11/21 = 248/273

Simplified Fraction

248/273

Mixed Number

Proper (248/273)

Decimal Value

0.908425

Percentage

90.8425%

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Step-by-Step Solution: 15/39 + 11/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 39 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 273 (which is smaller than their product 39 × 21 = 819, keeping the calculation simpler).

LCD(39, 21) = 273

Step 2

Convert to Equivalent Fractions with Common Denominator 273

Multiply the numerator and denominator of 15/39 by 7, and multiply the numerator and denominator of 11/21 by 13 so both fractions share the common base 273.

15 × 7/39 × 7 = 105/273 and 11 × 13/21 × 13 = 143/273

Step 3

Add the Numerators

Now add the numerators (105 + 143 = 248) and keep the common denominator 273 unchanged.

105 + 143/273 = 248/273

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 248 and 273 is 1, confirming that 248/273 cannot be reduced further—it is already in its simplest irreducible form.

248/273

Step 5

Decimal & Percentage Representation

Dividing the numerator 248 by denominator 273 produces a repeating decimal (approximately 0.908425, or 90.8425%).

248 ÷ 273 = 0.908425 (90.8425%)

Visual Representation

The diagram below illustrates 15/39 plus 11/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`248/273`
Mixed Number Form	`248/273`
Decimal Form	`0.908425`
Percentage	`90.8425%`

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Frequently Asked Questions

What is 15/39 plus 11/21 as a fraction?

15/39 + 11/21 in simplest fraction form is 248/273.

What is 15/39 plus 11/21 as a decimal?

15/39 + 11/21 converted to a decimal is 0.908425.

What is 15/39 plus 11/21 as a percentage?

15/39 + 11/21 expressed as a percentage is 90.8425%.

Does 15/39 plus 11/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.908425...) because the denominator contains prime factors other than 2 and 5.