What is 2/15 plus 8/21? (Answer: 18/35)

Exact Answer

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Problem: What is 2/15 plus 8/21?
Formula / Expression: 2/15 + 8/21
Final Answer: 18/35
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Step-by-Step Solution:

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

Step 2: Convert to Equivalent Fractions with Common Denominator 105
Multiply the numerator and denominator of 2/15 by 7, and multiply the numerator and denominator of 8/21 by 5 so both fractions share the common base 105.
Working: 2 × 7/15 × 7 = 14/105 and 8 × 5/21 × 5 = 40/105

Step 3: Add the Numerators
Now add the numerators (14 + 40 = 54) and keep the common denominator 105 unchanged.
Working: 14 + 40/105 = 54/105

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 54 and 105, which is 3. Divide both the numerator and denominator by 3.
Working: 54 ÷ 3/105 ÷ 3 = 18/35

Step 5: Decimal & Percentage Representation
Dividing the numerator 18 by denominator 35 produces a repeating decimal (approximately 0.514286, or 51.4286%).
Working: 18 ÷ 35 = 0.514286 (51.4286%)

Key Values:
- Simplified Fraction: 18/35
- Mixed Number Form: 18/35
- Decimal Value: 0.514286
- Percentage: 51.4286%

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Solved with FractionsCalc:
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2/15 + 8/21 = 18/35

Simplified Fraction

18/35

Mixed Number

Proper (18/35)

Decimal Value

0.514286

Percentage

51.4286%

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Step-by-Step Solution: 2/15 + 8/21

Step 1

Find the Least Common Denominator (LCD)

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

LCD(15, 21) = 105

Step 2

Convert to Equivalent Fractions with Common Denominator 105

Multiply the numerator and denominator of 2/15 by 7, and multiply the numerator and denominator of 8/21 by 5 so both fractions share the common base 105.

2 × 7/15 × 7 = 14/105 and 8 × 5/21 × 5 = 40/105

Step 3

Add the Numerators

Now add the numerators (14 + 40 = 54) and keep the common denominator 105 unchanged.

14 + 40/105 = 54/105

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 54 and 105, which is 3. Divide both the numerator and denominator by 3.

54 ÷ 3/105 ÷ 3 = 18/35

Step 5

Decimal & Percentage Representation

Dividing the numerator 18 by denominator 35 produces a repeating decimal (approximately 0.514286, or 51.4286%).

18 ÷ 35 = 0.514286 (51.4286%)

Visual Representation

The diagram below illustrates 2/15 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`18/35`
Mixed Number Form	`18/35`
Decimal Form	`0.514286`
Percentage	`51.4286%`

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Frequently Asked Questions

What is 2/15 plus 8/21 as a fraction?

2/15 + 8/21 in simplest fraction form is 18/35.

What is 2/15 plus 8/21 as a decimal?

2/15 + 8/21 converted to a decimal is 0.514286.

What is 2/15 plus 8/21 as a percentage?

2/15 + 8/21 expressed as a percentage is 51.4286%.

Does 2/15 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.514286...) because the denominator contains prime factors other than 2 and 5.