What is 11/30 plus 9/21? (Answer: 167/210)

Exact Answer

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Problem: What is 11/30 plus 9/21?
Formula / Expression: 11/30 + 9/21
Final Answer: 167/210
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).
Working: LCD(30, 21) = 210

Step 2: Convert to Equivalent Fractions with Common Denominator 210
Multiply the numerator and denominator of 11/30 by 7, and multiply the numerator and denominator of 9/21 by 10 so both fractions share the common base 210.
Working: 11 × 7/30 × 7 = 77/210 and 9 × 10/21 × 10 = 90/210

Step 3: Add the Numerators
Now add the numerators (77 + 90 = 167) and keep the common denominator 210 unchanged.
Working: 77 + 90/210 = 167/210

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 167 and 210 is 1, confirming that 167/210 cannot be reduced further—it is already in its simplest irreducible form.
Working: 167/210

Step 5: Decimal & Percentage Representation
Dividing the numerator 167 by denominator 210 produces a repeating decimal (approximately 0.795238, or 79.5238%).
Working: 167 ÷ 210 = 0.795238 (79.5238%)

Key Values:
- Simplified Fraction: 167/210
- Mixed Number Form: 167/210
- Decimal Value: 0.795238
- Percentage: 79.5238%

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Solved with FractionsCalc:
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11/30 + 9/21 = 167/210

Simplified Fraction

167/210

Mixed Number

Proper (167/210)

Decimal Value

0.795238

Percentage

79.5238%

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Step-by-Step Solution: 11/30 + 9/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).

LCD(30, 21) = 210

Step 2

Convert to Equivalent Fractions with Common Denominator 210

Multiply the numerator and denominator of 11/30 by 7, and multiply the numerator and denominator of 9/21 by 10 so both fractions share the common base 210.

11 × 7/30 × 7 = 77/210 and 9 × 10/21 × 10 = 90/210

Step 3

Add the Numerators

Now add the numerators (77 + 90 = 167) and keep the common denominator 210 unchanged.

77 + 90/210 = 167/210

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 167 and 210 is 1, confirming that 167/210 cannot be reduced further—it is already in its simplest irreducible form.

167/210

Step 5

Decimal & Percentage Representation

Dividing the numerator 167 by denominator 210 produces a repeating decimal (approximately 0.795238, or 79.5238%).

167 ÷ 210 = 0.795238 (79.5238%)

Visual Representation

The diagram below illustrates 11/30 plus 9/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`167/210`
Mixed Number Form	`167/210`
Decimal Form	`0.795238`
Percentage	`79.5238%`

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Frequently Asked Questions

What is 11/30 plus 9/21 as a fraction?

11/30 + 9/21 in simplest fraction form is 167/210.

What is 11/30 plus 9/21 as a decimal?

11/30 + 9/21 converted to a decimal is 0.795238.

What is 11/30 plus 9/21 as a percentage?

11/30 + 9/21 expressed as a percentage is 79.5238%.

Does 11/30 plus 9/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.795238...) because the denominator contains prime factors other than 2 and 5.