What is 21/41 plus 12/21? (Answer: 311/287)

Exact Answer

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Problem: What is 21/41 plus 12/21?
Formula / Expression: 21/41 + 12/21
Final Answer: 1 24/287 (311/287)
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 41 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 41 × 21 = 861.
Working: LCD(41, 21) = 861

Step 2: Convert to Equivalent Fractions with Common Denominator 861
Multiply the numerator and denominator of 21/41 by 21, and multiply the numerator and denominator of 12/21 by 41 so both fractions share the common base 861.
Working: 21 × 21/41 × 21 = 441/861 and 12 × 41/21 × 41 = 492/861

Step 3: Add the Numerators
Now add the numerators (441 + 492 = 933) and keep the common denominator 861 unchanged.
Working: 441 + 492/861 = 933/861

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 933 and 861, which is 3. Divide both the numerator and denominator by 3.
Working: 933 ÷ 3/861 ÷ 3 = 311/287

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (311) is greater than the denominator (287), divide 311 by 287: it goes in 1 whole time(s) with a remainder of 24, giving the mixed number 1 24/287.
Working: 311/287 = 1 24/287

Step 6: Decimal & Percentage Representation
Dividing the numerator 311 by denominator 287 produces a repeating decimal (approximately 1.083624, or 108.3624%).
Working: 311 ÷ 287 = 1.083624 (108.3624%)

Key Values:
- Simplified Fraction: 311/287
- Mixed Number Form: 1 24/287
- Decimal Value: 1.083624
- Percentage: 108.3624%

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Solved with FractionsCalc:
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21/41 + 12/21 = 311/287

Simplified Fraction

311/287

Mixed Number

1 24/287

Decimal Value

1.083624

Percentage

108.3624%

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Step-by-Step Solution: 21/41 + 12/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 41 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 41 × 21 = 861.

LCD(41, 21) = 861

Step 2

Convert to Equivalent Fractions with Common Denominator 861

Multiply the numerator and denominator of 21/41 by 21, and multiply the numerator and denominator of 12/21 by 41 so both fractions share the common base 861.

21 × 21/41 × 21 = 441/861 and 12 × 41/21 × 41 = 492/861

Step 3

Add the Numerators

Now add the numerators (441 + 492 = 933) and keep the common denominator 861 unchanged.

441 + 492/861 = 933/861

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 933 and 861, which is 3. Divide both the numerator and denominator by 3.

933 ÷ 3/861 ÷ 3 = 311/287

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (311) is greater than the denominator (287), divide 311 by 287: it goes in 1 whole time(s) with a remainder of 24, giving the mixed number 1 24/287.

311/287 = 124/287

Step 6

Decimal & Percentage Representation

Dividing the numerator 311 by denominator 287 produces a repeating decimal (approximately 1.083624, or 108.3624%).

311 ÷ 287 = 1.083624 (108.3624%)

Visual Representation

The diagram below illustrates 21/41 plus 12/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`311/287`
Mixed Number Form	`1 24/287`
Decimal Form	`1.083624`
Percentage	`108.3624%`

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Frequently Asked Questions

What is 21/41 plus 12/21 as a fraction?

21/41 + 12/21 in simplest fraction form is 311/287 (or 1 24/287 as a mixed number).

What is 21/41 plus 12/21 as a decimal?

21/41 + 12/21 converted to a decimal is 1.083624.

What is 21/41 plus 12/21 as a percentage?

21/41 + 12/21 expressed as a percentage is 108.3624%.

How do you write 21/41 plus 12/21 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 311/287 can be written as the mixed number 1 24/287.

Does 21/41 plus 12/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.083624...) because the denominator contains prime factors other than 2 and 5.