What is 2/9 minus 8/21? (Answer: -10/63)

Exact Answer

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Problem: What is 2/9 minus 8/21?
Formula / Expression: 2/9 − 8/21
Final Answer: -10/63
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 9 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 63 (which is smaller than their product 9 × 21 = 189, keeping the calculation simpler).
Working: LCD(9, 21) = 63

Step 2: Convert to Equivalent Fractions with Common Denominator 63
Multiply the numerator and denominator of 2/9 by 7, and multiply the numerator and denominator of 8/21 by 3 so both fractions share the common base 63.
Working: 2 × 7/9 × 7 = 14/63 and 8 × 3/21 × 3 = 24/63

Step 3: Subtract the Numerators
Now subtract the numerators (14 − 24 = -10) and keep the common denominator 63 unchanged.
Working: 14 − 24/63 = -10/63

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 10 and 63 is 1, confirming that -10/63 cannot be reduced further—it is already in its simplest irreducible form.
Working: -10/63

Step 5: Decimal & Percentage Representation
Dividing the numerator -10 by denominator 63 produces a repeating decimal (approximately -0.15873, or -15.873%).
Working: -10 ÷ 63 = -0.15873 (-15.873%)

Key Values:
- Simplified Fraction: -10/63
- Mixed Number Form: -10/63
- Decimal Value: -0.15873
- Percentage: -15.873%

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Solved with FractionsCalc:
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2/9 − 8/21 = -10/63

Simplified Fraction

-10/63

Mixed Number

Proper (-10/63)

Decimal Value

-0.15873

Percentage

-15.873%

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Step-by-Step Solution: 2/9 − 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 9 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 63 (which is smaller than their product 9 × 21 = 189, keeping the calculation simpler).

LCD(9, 21) = 63

Step 2

Convert to Equivalent Fractions with Common Denominator 63

Multiply the numerator and denominator of 2/9 by 7, and multiply the numerator and denominator of 8/21 by 3 so both fractions share the common base 63.

2 × 7/9 × 7 = 14/63 and 8 × 3/21 × 3 = 24/63

Step 3

Subtract the Numerators

Now subtract the numerators (14 − 24 = -10) and keep the common denominator 63 unchanged.

14 − 24/63 = -10/63

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 10 and 63 is 1, confirming that -10/63 cannot be reduced further—it is already in its simplest irreducible form.

-10/63

Step 5

Decimal & Percentage Representation

Dividing the numerator -10 by denominator 63 produces a repeating decimal (approximately -0.15873, or -15.873%).

-10 ÷ 63 = -0.15873 (-15.873%)

Visual Representation

The diagram below illustrates 2/9 minus 8/21 visually:

−

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`-10/63`
Mixed Number Form	`-10/63`
Decimal Form	`-0.15873`
Percentage	`-15.873%`

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Frequently Asked Questions

What is 2/9 minus 8/21 as a fraction?

2/9 − 8/21 in simplest fraction form is -10/63.

What is 2/9 minus 8/21 as a decimal?

2/9 − 8/21 converted to a decimal is -0.15873.

What is 2/9 minus 8/21 as a percentage?

2/9 − 8/21 expressed as a percentage is -15.873%.

Does 2/9 minus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately -0.15873...) because the denominator contains prime factors other than 2 and 5.