What is 7/39 plus 8/21? (Answer: 51/91)

Exact Answer

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Problem: What is 7/39 plus 8/21?
Formula / Expression: 7/39 + 8/21
Final Answer: 51/91
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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 7/39 by 7, and multiply the numerator and denominator of 8/21 by 13 so both fractions share the common base 273.
Working: 7 × 7/39 × 7 = 49/273 and 8 × 13/21 × 13 = 104/273

Step 3: Add the Numerators
Now add the numerators (49 + 104 = 153) and keep the common denominator 273 unchanged.
Working: 49 + 104/273 = 153/273

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 153 and 273, which is 3. Divide both the numerator and denominator by 3.
Working: 153 ÷ 3/273 ÷ 3 = 51/91

Step 5: Decimal & Percentage Representation
Dividing the numerator 51 by denominator 91 produces a repeating decimal (approximately 0.56044, or 56.044%).
Working: 51 ÷ 91 = 0.56044 (56.044%)

Key Values:
- Simplified Fraction: 51/91
- Mixed Number Form: 51/91
- Decimal Value: 0.56044
- Percentage: 56.044%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-7-39-plus-8-21/
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7/39 + 8/21 = 51/91

Simplified Fraction

51/91

Mixed Number

Proper (51/91)

Decimal Value

0.56044

Percentage

56.044%

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Step-by-Step Solution: 7/39 + 8/21

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 7/39 by 7, and multiply the numerator and denominator of 8/21 by 13 so both fractions share the common base 273.

7 × 7/39 × 7 = 49/273 and 8 × 13/21 × 13 = 104/273

Step 3

Add the Numerators

Now add the numerators (49 + 104 = 153) and keep the common denominator 273 unchanged.

49 + 104/273 = 153/273

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 153 and 273, which is 3. Divide both the numerator and denominator by 3.

153 ÷ 3/273 ÷ 3 = 51/91

Step 5

Decimal & Percentage Representation

Dividing the numerator 51 by denominator 91 produces a repeating decimal (approximately 0.56044, or 56.044%).

51 ÷ 91 = 0.56044 (56.044%)

Visual Representation

The diagram below illustrates 7/39 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`51/91`
Mixed Number Form	`51/91`
Decimal Form	`0.56044`
Percentage	`56.044%`

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Frequently Asked Questions

What is 7/39 plus 8/21 as a fraction?

7/39 + 8/21 in simplest fraction form is 51/91.

What is 7/39 plus 8/21 as a decimal?

7/39 + 8/21 converted to a decimal is 0.56044.

What is 7/39 plus 8/21 as a percentage?

7/39 + 8/21 expressed as a percentage is 56.044%.

Does 7/39 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.56044...) because the denominator contains prime factors other than 2 and 5.