What is 11/28 plus 9/21? (Answer: 23/28)

Exact Answer

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Problem: What is 11/28 plus 9/21?
Formula / Expression: 11/28 + 9/21
Final Answer: 23/28
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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 11/28 by 3, and multiply the numerator and denominator of 9/21 by 4 so both fractions share the common base 84.
Working: 11 × 3/28 × 3 = 33/84 and 9 × 4/21 × 4 = 36/84

Step 3: Add the Numerators
Now add the numerators (33 + 36 = 69) and keep the common denominator 84 unchanged.
Working: 33 + 36/84 = 69/84

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 69 and 84, which is 3. Divide both the numerator and denominator by 3.
Working: 69 ÷ 3/84 ÷ 3 = 23/28

Step 5: Decimal & Percentage Representation
Dividing the numerator 23 by denominator 28 produces a repeating decimal (approximately 0.821429, or 82.1429%).
Working: 23 ÷ 28 = 0.821429 (82.1429%)

Key Values:
- Simplified Fraction: 23/28
- Mixed Number Form: 23/28
- Decimal Value: 0.821429
- Percentage: 82.1429%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-11-28-plus-9-21/
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11/28 + 9/21 = 23/28

Simplified Fraction

23/28

Mixed Number

Proper (23/28)

Decimal Value

0.821429

Percentage

82.1429%

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Step-by-Step Solution: 11/28 + 9/21

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 11/28 by 3, and multiply the numerator and denominator of 9/21 by 4 so both fractions share the common base 84.

11 × 3/28 × 3 = 33/84 and 9 × 4/21 × 4 = 36/84

Step 3

Add the Numerators

Now add the numerators (33 + 36 = 69) and keep the common denominator 84 unchanged.

33 + 36/84 = 69/84

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 69 and 84, which is 3. Divide both the numerator and denominator by 3.

69 ÷ 3/84 ÷ 3 = 23/28

Step 5

Decimal & Percentage Representation

Dividing the numerator 23 by denominator 28 produces a repeating decimal (approximately 0.821429, or 82.1429%).

23 ÷ 28 = 0.821429 (82.1429%)

Visual Representation

The diagram below illustrates 11/28 plus 9/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`23/28`
Mixed Number Form	`23/28`
Decimal Form	`0.821429`
Percentage	`82.1429%`

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Frequently Asked Questions

What is 11/28 plus 9/21 as a fraction?

11/28 + 9/21 in simplest fraction form is 23/28.

What is 11/28 plus 9/21 as a decimal?

11/28 + 9/21 converted to a decimal is 0.821429.

What is 11/28 plus 9/21 as a percentage?

11/28 + 9/21 expressed as a percentage is 82.1429%.

Does 11/28 plus 9/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.821429...) because the denominator contains prime factors other than 2 and 5.