What is 12/53 plus 9/21? (Answer: 243/371)

Exact Answer

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Problem: What is 12/53 plus 9/21?
Formula / Expression: 12/53 + 9/21
Final Answer: 243/371
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 53 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 53 × 21 = 1113.
Working: LCD(53, 21) = 1113

Step 2: Convert to Equivalent Fractions with Common Denominator 1113
Multiply the numerator and denominator of 12/53 by 21, and multiply the numerator and denominator of 9/21 by 53 so both fractions share the common base 1113.
Working: 12 × 21/53 × 21 = 252/1113 and 9 × 53/21 × 53 = 477/1113

Step 3: Add the Numerators
Now add the numerators (252 + 477 = 729) and keep the common denominator 1113 unchanged.
Working: 252 + 477/1113 = 729/1113

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 729 and 1113, which is 3. Divide both the numerator and denominator by 3.
Working: 729 ÷ 3/1113 ÷ 3 = 243/371

Step 5: Decimal & Percentage Representation
Dividing the numerator 243 by denominator 371 produces a repeating decimal (approximately 0.654987, or 65.4987%).
Working: 243 ÷ 371 = 0.654987 (65.4987%)

Key Values:
- Simplified Fraction: 243/371
- Mixed Number Form: 243/371
- Decimal Value: 0.654987
- Percentage: 65.4987%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-12-53-plus-9-21/
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12/53 + 9/21 = 243/371

Simplified Fraction

243/371

Mixed Number

Proper (243/371)

Decimal Value

0.654987

Percentage

65.4987%

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Step-by-Step Solution: 12/53 + 9/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 53 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 53 × 21 = 1113.

LCD(53, 21) = 1113

Step 2

Convert to Equivalent Fractions with Common Denominator 1113

Multiply the numerator and denominator of 12/53 by 21, and multiply the numerator and denominator of 9/21 by 53 so both fractions share the common base 1113.

12 × 21/53 × 21 = 252/1113 and 9 × 53/21 × 53 = 477/1113

Step 3

Add the Numerators

Now add the numerators (252 + 477 = 729) and keep the common denominator 1113 unchanged.

252 + 477/1113 = 729/1113

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 729 and 1113, which is 3. Divide both the numerator and denominator by 3.

729 ÷ 3/1113 ÷ 3 = 243/371

Step 5

Decimal & Percentage Representation

Dividing the numerator 243 by denominator 371 produces a repeating decimal (approximately 0.654987, or 65.4987%).

243 ÷ 371 = 0.654987 (65.4987%)

Visual Representation

The diagram below illustrates 12/53 plus 9/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`243/371`
Mixed Number Form	`243/371`
Decimal Form	`0.654987`
Percentage	`65.4987%`

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Frequently Asked Questions

What is 12/53 plus 9/21 as a fraction?

12/53 + 9/21 in simplest fraction form is 243/371.

What is 12/53 plus 9/21 as a decimal?

12/53 + 9/21 converted to a decimal is 0.654987.

What is 12/53 plus 9/21 as a percentage?

12/53 + 9/21 expressed as a percentage is 65.4987%.

Does 12/53 plus 9/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.654987...) because the denominator contains prime factors other than 2 and 5.