What is 8/20 plus 12/21? (Answer: 34/35)

Exact Answer

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Problem: What is 8/20 plus 12/21?
Formula / Expression: 8/20 + 12/21
Final Answer: 34/35
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 20 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 20 × 21 = 420.
Working: LCD(20, 21) = 420

Step 2: Convert to Equivalent Fractions with Common Denominator 420
Multiply the numerator and denominator of 8/20 by 21, and multiply the numerator and denominator of 12/21 by 20 so both fractions share the common base 420.
Working: 8 × 21/20 × 21 = 168/420 and 12 × 20/21 × 20 = 240/420

Step 3: Add the Numerators
Now add the numerators (168 + 240 = 408) and keep the common denominator 420 unchanged.
Working: 168 + 240/420 = 408/420

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 408 and 420, which is 12. Divide both the numerator and denominator by 12.
Working: 408 ÷ 12/420 ÷ 12 = 34/35

Step 5: Decimal & Percentage Representation
Dividing the numerator 34 by denominator 35 produces a repeating decimal (approximately 0.971429, or 97.1429%).
Working: 34 ÷ 35 = 0.971429 (97.1429%)

Key Values:
- Simplified Fraction: 34/35
- Mixed Number Form: 34/35
- Decimal Value: 0.971429
- Percentage: 97.1429%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-8-20-plus-12-21/
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8/20 + 12/21 = 34/35

Simplified Fraction

34/35

Mixed Number

Proper (34/35)

Decimal Value

0.971429

Percentage

97.1429%

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Step-by-Step Solution: 8/20 + 12/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 20 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 20 × 21 = 420.

LCD(20, 21) = 420

Step 2

Convert to Equivalent Fractions with Common Denominator 420

Multiply the numerator and denominator of 8/20 by 21, and multiply the numerator and denominator of 12/21 by 20 so both fractions share the common base 420.

8 × 21/20 × 21 = 168/420 and 12 × 20/21 × 20 = 240/420

Step 3

Add the Numerators

Now add the numerators (168 + 240 = 408) and keep the common denominator 420 unchanged.

168 + 240/420 = 408/420

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 408 and 420, which is 12. Divide both the numerator and denominator by 12.

408 ÷ 12/420 ÷ 12 = 34/35

Step 5

Decimal & Percentage Representation

Dividing the numerator 34 by denominator 35 produces a repeating decimal (approximately 0.971429, or 97.1429%).

34 ÷ 35 = 0.971429 (97.1429%)

Visual Representation

The diagram below illustrates 8/20 plus 12/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`34/35`
Mixed Number Form	`34/35`
Decimal Form	`0.971429`
Percentage	`97.1429%`

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Frequently Asked Questions

What is 8/20 plus 12/21 as a fraction?

8/20 + 12/21 in simplest fraction form is 34/35.

What is 8/20 plus 12/21 as a decimal?

8/20 + 12/21 converted to a decimal is 0.971429.

What is 8/20 plus 12/21 as a percentage?

8/20 + 12/21 expressed as a percentage is 97.1429%.

Does 8/20 plus 12/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.971429...) because the denominator contains prime factors other than 2 and 5.