What is 12/28 plus 11/21? (Answer: 20/21)

Exact Answer

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Problem: What is 12/28 plus 11/21?
Formula / Expression: 12/28 + 11/21
Final Answer: 20/21
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 28 and 21 share a common factor (GCD = 7). Finding their Least Common Multiple gives an LCD of 84 (which is smaller than their product 28 × 21 = 588, keeping the calculation simpler).
Working: LCD(28, 21) = 84

Step 2: Convert to Equivalent Fractions with Common Denominator 84
Multiply the numerator and denominator of 12/28 by 3, and multiply the numerator and denominator of 11/21 by 4 so both fractions share the common base 84.
Working: 12 × 3/28 × 3 = 36/84 and 11 × 4/21 × 4 = 44/84

Step 3: Add the Numerators
Now add the numerators (36 + 44 = 80) and keep the common denominator 84 unchanged.
Working: 36 + 44/84 = 80/84

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 80 and 84, which is 4. Divide both the numerator and denominator by 4.
Working: 80 ÷ 4/84 ÷ 4 = 20/21

Step 5: Decimal & Percentage Representation
Dividing the numerator 20 by denominator 21 produces a repeating decimal (approximately 0.952381, or 95.2381%).
Working: 20 ÷ 21 = 0.952381 (95.2381%)

Key Values:
- Simplified Fraction: 20/21
- Mixed Number Form: 20/21
- Decimal Value: 0.952381
- Percentage: 95.2381%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-12-28-plus-11-21/
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12/28 + 11/21 = 20/21

Simplified Fraction

20/21

Mixed Number

Proper (20/21)

Decimal Value

0.952381

Percentage

95.2381%

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Step-by-Step Solution: 12/28 + 11/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 28 and 21 share a common factor (GCD = 7). Finding their Least Common Multiple gives an LCD of 84 (which is smaller than their product 28 × 21 = 588, keeping the calculation simpler).

LCD(28, 21) = 84

Step 2

Convert to Equivalent Fractions with Common Denominator 84

Multiply the numerator and denominator of 12/28 by 3, and multiply the numerator and denominator of 11/21 by 4 so both fractions share the common base 84.

12 × 3/28 × 3 = 36/84 and 11 × 4/21 × 4 = 44/84

Step 3

Add the Numerators

Now add the numerators (36 + 44 = 80) and keep the common denominator 84 unchanged.

36 + 44/84 = 80/84

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 80 and 84, which is 4. Divide both the numerator and denominator by 4.

80 ÷ 4/84 ÷ 4 = 20/21

Step 5

Decimal & Percentage Representation

Dividing the numerator 20 by denominator 21 produces a repeating decimal (approximately 0.952381, or 95.2381%).

20 ÷ 21 = 0.952381 (95.2381%)

Visual Representation

The diagram below illustrates 12/28 plus 11/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`20/21`
Mixed Number Form	`20/21`
Decimal Form	`0.952381`
Percentage	`95.2381%`

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Frequently Asked Questions

What is 12/28 plus 11/21 as a fraction?

12/28 + 11/21 in simplest fraction form is 20/21.

What is 12/28 plus 11/21 as a decimal?

12/28 + 11/21 converted to a decimal is 0.952381.

What is 12/28 plus 11/21 as a percentage?

12/28 + 11/21 expressed as a percentage is 95.2381%.

Does 12/28 plus 11/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.952381...) because the denominator contains prime factors other than 2 and 5.