What is 5/21 plus 4/15? (Answer: 53/105)

Exact Answer

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Problem: What is 5/21 plus 4/15?
Formula / Expression: 5/21 + 4/15
Final Answer: 53/105
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 21 and 15 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 105 (which is smaller than their product 21 × 15 = 315, keeping the calculation simpler).
Working: LCD(21, 15) = 105

Step 2: Convert to Equivalent Fractions with Common Denominator 105
Multiply the numerator and denominator of 5/21 by 5, and multiply the numerator and denominator of 4/15 by 7 so both fractions share the common base 105.
Working: 5 × 5/21 × 5 = 25/105 and 4 × 7/15 × 7 = 28/105

Step 3: Add the Numerators
Now add the numerators (25 + 28 = 53) and keep the common denominator 105 unchanged.
Working: 25 + 28/105 = 53/105

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 53 and 105 is 1, confirming that 53/105 cannot be reduced further—it is already in its simplest irreducible form.
Working: 53/105

Step 5: Decimal & Percentage Representation
Dividing the numerator 53 by denominator 105 produces a repeating decimal (approximately 0.504762, or 50.4762%).
Working: 53 ÷ 105 = 0.504762 (50.4762%)

Key Values:
- Simplified Fraction: 53/105
- Mixed Number Form: 53/105
- Decimal Value: 0.504762
- Percentage: 50.4762%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-5-21-plus-4-15/
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5/21 + 4/15 = 53/105

Simplified Fraction

53/105

Mixed Number

Proper (53/105)

Decimal Value

0.504762

Percentage

50.4762%

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Step-by-Step Solution: 5/21 + 4/15

Step 1

Find the Least Common Denominator (LCD)

The denominators 21 and 15 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 105 (which is smaller than their product 21 × 15 = 315, keeping the calculation simpler).

LCD(21, 15) = 105

Step 2

Convert to Equivalent Fractions with Common Denominator 105

Multiply the numerator and denominator of 5/21 by 5, and multiply the numerator and denominator of 4/15 by 7 so both fractions share the common base 105.

5 × 5/21 × 5 = 25/105 and 4 × 7/15 × 7 = 28/105

Step 3

Add the Numerators

Now add the numerators (25 + 28 = 53) and keep the common denominator 105 unchanged.

25 + 28/105 = 53/105

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 53 and 105 is 1, confirming that 53/105 cannot be reduced further—it is already in its simplest irreducible form.

53/105

Step 5

Decimal & Percentage Representation

Dividing the numerator 53 by denominator 105 produces a repeating decimal (approximately 0.504762, or 50.4762%).

53 ÷ 105 = 0.504762 (50.4762%)

Visual Representation

The diagram below illustrates 5/21 plus 4/15 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`53/105`
Mixed Number Form	`53/105`
Decimal Form	`0.504762`
Percentage	`50.4762%`

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Frequently Asked Questions

What is 5/21 plus 4/15 as a fraction?

5/21 + 4/15 in simplest fraction form is 53/105.

What is 5/21 plus 4/15 as a decimal?

5/21 + 4/15 converted to a decimal is 0.504762.

What is 5/21 plus 4/15 as a percentage?

5/21 + 4/15 expressed as a percentage is 50.4762%.

Does 5/21 plus 4/15 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.504762...) because the denominator contains prime factors other than 2 and 5.