What is 4/21 plus 8/42? (Answer: 8/21)

Exact Answer

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Problem: What is 4/21 plus 8/42?
Formula / Expression: 4/21 + 8/42
Final Answer: 8/21
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
Notice that 42 is an exact multiple of 21 (21 × 2 = 42). The Least Common Denominator (LCD) is simply 42, meaning we only need to scale one fraction.
Working: LCD(21, 42) = 42

Step 2: Convert to Equivalent Fractions with Common Denominator 42
Multiply the numerator and denominator of 4/21 by 2, and multiply the numerator and denominator of 8/42 by 1 so both fractions share the common base 42.
Working: 4 × 2/21 × 2 = 8/42 and 8 × 1/42 × 1 = 8/42

Step 3: Add the Numerators
Now add the numerators (8 + 8 = 16) and keep the common denominator 42 unchanged.
Working: 8 + 8/42 = 16/42

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 16 and 42, which is 2. Divide both the numerator and denominator by 2.
Working: 16 ÷ 2/42 ÷ 2 = 8/21

Step 5: Decimal & Percentage Representation
Dividing the numerator 8 by denominator 21 produces a repeating decimal (approximately 0.380952, or 38.0952%).
Working: 8 ÷ 21 = 0.380952 (38.0952%)

Key Values:
- Simplified Fraction: 8/21
- Mixed Number Form: 8/21
- Decimal Value: 0.380952
- Percentage: 38.0952%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-4-21-plus-8-42/
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4/21 + 8/42 = 8/21

Simplified Fraction

8/21

Mixed Number

Proper (8/21)

Decimal Value

0.380952

Percentage

38.0952%

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Step-by-Step Solution: 4/21 + 8/42

Step 1

Find the Least Common Denominator (LCD)

Notice that 42 is an exact multiple of 21 (21 × 2 = 42). The Least Common Denominator (LCD) is simply 42, meaning we only need to scale one fraction.

LCD(21, 42) = 42

Step 2

Convert to Equivalent Fractions with Common Denominator 42

Multiply the numerator and denominator of 4/21 by 2, and multiply the numerator and denominator of 8/42 by 1 so both fractions share the common base 42.

4 × 2/21 × 2 = 8/42 and 8 × 1/42 × 1 = 8/42

Step 3

Add the Numerators

Now add the numerators (8 + 8 = 16) and keep the common denominator 42 unchanged.

8 + 8/42 = 16/42

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 16 and 42, which is 2. Divide both the numerator and denominator by 2.

16 ÷ 2/42 ÷ 2 = 8/21

Step 5

Decimal & Percentage Representation

Dividing the numerator 8 by denominator 21 produces a repeating decimal (approximately 0.380952, or 38.0952%).

8 ÷ 21 = 0.380952 (38.0952%)

Visual Representation

The diagram below illustrates 4/21 plus 8/42 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`8/21`
Mixed Number Form	`8/21`
Decimal Form	`0.380952`
Percentage	`38.0952%`

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Frequently Asked Questions

What is 4/21 plus 8/42 as a fraction?

4/21 + 8/42 in simplest fraction form is 8/21.

What is 4/21 plus 8/42 as a decimal?

4/21 + 8/42 converted to a decimal is 0.380952.

What is 4/21 plus 8/42 as a percentage?

4/21 + 8/42 expressed as a percentage is 38.0952%.

Does 4/21 plus 8/42 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.380952...) because the denominator contains prime factors other than 2 and 5.