What is 12/30 plus 12/21? (Answer: 34/35)

Exact Answer

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Problem: What is 12/30 plus 12/21?
Formula / Expression: 12/30 + 12/21
Final Answer: 34/35
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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 12/30 by 7, and multiply the numerator and denominator of 12/21 by 10 so both fractions share the common base 210.
Working: 12 × 7/30 × 7 = 84/210 and 12 × 10/21 × 10 = 120/210

Step 3: Add the Numerators
Now add the numerators (84 + 120 = 204) and keep the common denominator 210 unchanged.
Working: 84 + 120/210 = 204/210

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 204 and 210, which is 6. Divide both the numerator and denominator by 6.
Working: 204 ÷ 6/210 ÷ 6 = 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-12-30-plus-12-21/
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12/30 + 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: 12/30 + 12/21

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 12/30 by 7, and multiply the numerator and denominator of 12/21 by 10 so both fractions share the common base 210.

12 × 7/30 × 7 = 84/210 and 12 × 10/21 × 10 = 120/210

Step 3

Add the Numerators

Now add the numerators (84 + 120 = 204) and keep the common denominator 210 unchanged.

84 + 120/210 = 204/210

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 204 and 210, which is 6. Divide both the numerator and denominator by 6.

204 ÷ 6/210 ÷ 6 = 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 12/30 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 12/30 plus 12/21 as a fraction?

12/30 + 12/21 in simplest fraction form is 34/35.

What is 12/30 plus 12/21 as a decimal?

12/30 + 12/21 converted to a decimal is 0.971429.

What is 12/30 plus 12/21 as a percentage?

12/30 + 12/21 expressed as a percentage is 97.1429%.

Does 12/30 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.