What is 5/21 plus 2/4? (Answer: 31/42)

Exact Answer

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Problem: What is 5/21 plus 2/4?
Formula / Expression: 5/21 + 2/4
Final Answer: 31/42
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 21 and 4 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 21 × 4 = 84.
Working: LCD(21, 4) = 84

Step 2: Convert to Equivalent Fractions with Common Denominator 84
Multiply the numerator and denominator of 5/21 by 4, and multiply the numerator and denominator of 2/4 by 21 so both fractions share the common base 84.
Working: 5 × 4/21 × 4 = 20/84 and 2 × 21/4 × 21 = 42/84

Step 3: Add the Numerators
Now add the numerators (20 + 42 = 62) and keep the common denominator 84 unchanged.
Working: 20 + 42/84 = 62/84

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 62 and 84, which is 2. Divide both the numerator and denominator by 2.
Working: 62 ÷ 2/84 ÷ 2 = 31/42

Step 5: Decimal & Percentage Representation
Dividing the numerator 31 by denominator 42 produces a repeating decimal (approximately 0.738095, or 73.8095%).
Working: 31 ÷ 42 = 0.738095 (73.8095%)

Key Values:
- Simplified Fraction: 31/42
- Mixed Number Form: 31/42
- Decimal Value: 0.738095
- Percentage: 73.8095%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-5-21-plus-2-4/
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5/21 + 2/4 = 31/42

Simplified Fraction

31/42

Mixed Number

Proper (31/42)

Decimal Value

0.738095

Percentage

73.8095%

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Step-by-Step Solution: 5/21 + 2/4

Step 1

Find the Least Common Denominator (LCD)

The denominators 21 and 4 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 21 × 4 = 84.

LCD(21, 4) = 84

Step 2

Convert to Equivalent Fractions with Common Denominator 84

Multiply the numerator and denominator of 5/21 by 4, and multiply the numerator and denominator of 2/4 by 21 so both fractions share the common base 84.

5 × 4/21 × 4 = 20/84 and 2 × 21/4 × 21 = 42/84

Step 3

Add the Numerators

Now add the numerators (20 + 42 = 62) and keep the common denominator 84 unchanged.

20 + 42/84 = 62/84

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 62 and 84, which is 2. Divide both the numerator and denominator by 2.

62 ÷ 2/84 ÷ 2 = 31/42

Step 5

Decimal & Percentage Representation

Dividing the numerator 31 by denominator 42 produces a repeating decimal (approximately 0.738095, or 73.8095%).

31 ÷ 42 = 0.738095 (73.8095%)

Visual Representation

The diagram below illustrates 5/21 plus 2/4 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`31/42`
Mixed Number Form	`31/42`
Decimal Form	`0.738095`
Percentage	`73.8095%`

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Frequently Asked Questions

What is 5/21 plus 2/4 as a fraction?

5/21 + 2/4 in simplest fraction form is 31/42.

What is 5/21 plus 2/4 as a decimal?

5/21 + 2/4 converted to a decimal is 0.738095.

What is 5/21 plus 2/4 as a percentage?

5/21 + 2/4 expressed as a percentage is 73.8095%.

Does 5/21 plus 2/4 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.738095...) because the denominator contains prime factors other than 2 and 5.