What is 15/30 plus 15/21? (Answer: 17/14)

Exact Answer

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Problem: What is 15/30 plus 15/21?
Formula / Expression: 15/30 + 15/21
Final Answer: 1 3/14 (17/14)
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).
Working: LCD(30, 21) = 210

Step 2: Convert to Equivalent Fractions with Common Denominator 210
Multiply the numerator and denominator of 15/30 by 7, and multiply the numerator and denominator of 15/21 by 10 so both fractions share the common base 210.
Working: 15 × 7/30 × 7 = 105/210 and 15 × 10/21 × 10 = 150/210

Step 3: Add the Numerators
Now add the numerators (105 + 150 = 255) and keep the common denominator 210 unchanged.
Working: 105 + 150/210 = 255/210

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 255 and 210, which is 15. Divide both the numerator and denominator by 15.
Working: 255 ÷ 15/210 ÷ 15 = 17/14

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (17) is greater than the denominator (14), divide 17 by 14: it goes in 1 whole time(s) with a remainder of 3, giving the mixed number 1 3/14.
Working: 17/14 = 1 3/14

Step 6: Decimal & Percentage Representation
Dividing the numerator 17 by denominator 14 produces a repeating decimal (approximately 1.214286, or 121.4286%).
Working: 17 ÷ 14 = 1.214286 (121.4286%)

Key Values:
- Simplified Fraction: 17/14
- Mixed Number Form: 1 3/14
- Decimal Value: 1.214286
- Percentage: 121.4286%

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15/30 + 15/21 = 17/14

Simplified Fraction

17/14

Mixed Number

1 3/14

Decimal Value

1.214286

Percentage

121.4286%

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Step-by-Step Solution: 15/30 + 15/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).

LCD(30, 21) = 210

Step 2

Convert to Equivalent Fractions with Common Denominator 210

Multiply the numerator and denominator of 15/30 by 7, and multiply the numerator and denominator of 15/21 by 10 so both fractions share the common base 210.

15 × 7/30 × 7 = 105/210 and 15 × 10/21 × 10 = 150/210

Step 3

Add the Numerators

Now add the numerators (105 + 150 = 255) and keep the common denominator 210 unchanged.

105 + 150/210 = 255/210

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 255 and 210, which is 15. Divide both the numerator and denominator by 15.

255 ÷ 15/210 ÷ 15 = 17/14

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (17) is greater than the denominator (14), divide 17 by 14: it goes in 1 whole time(s) with a remainder of 3, giving the mixed number 1 3/14.

17/14 = 13/14

Step 6

Decimal & Percentage Representation

Dividing the numerator 17 by denominator 14 produces a repeating decimal (approximately 1.214286, or 121.4286%).

17 ÷ 14 = 1.214286 (121.4286%)

Visual Representation

The diagram below illustrates 15/30 plus 15/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`17/14`
Mixed Number Form	`1 3/14`
Decimal Form	`1.214286`
Percentage	`121.4286%`

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Frequently Asked Questions

What is 15/30 plus 15/21 as a fraction?

15/30 + 15/21 in simplest fraction form is 17/14 (or 1 3/14 as a mixed number).

What is 15/30 plus 15/21 as a decimal?

15/30 + 15/21 converted to a decimal is 1.214286.

What is 15/30 plus 15/21 as a percentage?

15/30 + 15/21 expressed as a percentage is 121.4286%.

How do you write 15/30 plus 15/21 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 17/14 can be written as the mixed number 1 3/14.

Does 15/30 plus 15/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.214286...) because the denominator contains prime factors other than 2 and 5.