What is 8/63 plus 4/21? (Answer: 20/63)

Exact Answer

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Problem: What is 8/63 plus 4/21?
Formula / Expression: 8/63 + 4/21
Final Answer: 20/63
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
Notice that 63 is an exact multiple of 21 (21 × 3 = 63). The Least Common Denominator (LCD) is simply 63, meaning we only need to scale one fraction.
Working: LCD(63, 21) = 63

Step 2: Convert to Equivalent Fractions with Common Denominator 63
Multiply the numerator and denominator of 8/63 by 1, and multiply the numerator and denominator of 4/21 by 3 so both fractions share the common base 63.
Working: 8 × 1/63 × 1 = 8/63 and 4 × 3/21 × 3 = 12/63

Step 3: Add the Numerators
Now add the numerators (8 + 12 = 20) and keep the common denominator 63 unchanged.
Working: 8 + 12/63 = 20/63

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 20 and 63 is 1, confirming that 20/63 cannot be reduced further—it is already in its simplest irreducible form.
Working: 20/63

Step 5: Decimal & Percentage Representation
Dividing the numerator 20 by denominator 63 produces a repeating decimal (approximately 0.31746, or 31.746%).
Working: 20 ÷ 63 = 0.31746 (31.746%)

Key Values:
- Simplified Fraction: 20/63
- Mixed Number Form: 20/63
- Decimal Value: 0.31746
- Percentage: 31.746%

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Solved with FractionsCalc:
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8/63 + 4/21 = 20/63

Simplified Fraction

20/63

Mixed Number

Proper (20/63)

Decimal Value

0.31746

Percentage

31.746%

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Step-by-Step Solution: 8/63 + 4/21

Step 1

Find the Least Common Denominator (LCD)

Notice that 63 is an exact multiple of 21 (21 × 3 = 63). The Least Common Denominator (LCD) is simply 63, meaning we only need to scale one fraction.

LCD(63, 21) = 63

Step 2

Convert to Equivalent Fractions with Common Denominator 63

Multiply the numerator and denominator of 8/63 by 1, and multiply the numerator and denominator of 4/21 by 3 so both fractions share the common base 63.

8 × 1/63 × 1 = 8/63 and 4 × 3/21 × 3 = 12/63

Step 3

Add the Numerators

Now add the numerators (8 + 12 = 20) and keep the common denominator 63 unchanged.

8 + 12/63 = 20/63

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 20 and 63 is 1, confirming that 20/63 cannot be reduced further—it is already in its simplest irreducible form.

20/63

Step 5

Decimal & Percentage Representation

Dividing the numerator 20 by denominator 63 produces a repeating decimal (approximately 0.31746, or 31.746%).

20 ÷ 63 = 0.31746 (31.746%)

Visual Representation

The diagram below illustrates 8/63 plus 4/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`20/63`
Mixed Number Form	`20/63`
Decimal Form	`0.31746`
Percentage	`31.746%`

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Frequently Asked Questions

What is 8/63 plus 4/21 as a fraction?

8/63 + 4/21 in simplest fraction form is 20/63.

What is 8/63 plus 4/21 as a decimal?

8/63 + 4/21 converted to a decimal is 0.31746.

What is 8/63 plus 4/21 as a percentage?

8/63 + 4/21 expressed as a percentage is 31.746%.

Does 8/63 plus 4/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.31746...) because the denominator contains prime factors other than 2 and 5.