What is 4/9 minus 10/21? (Answer: -2/63)

Exact Answer

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Problem: What is 4/9 minus 10/21?
Formula / Expression: 4/9 − 10/21
Final Answer: -2/63
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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 4/9 by 7, and multiply the numerator and denominator of 10/21 by 3 so both fractions share the common base 63.
Working: 4 × 7/9 × 7 = 28/63 and 10 × 3/21 × 3 = 30/63

Step 3: Subtract the Numerators
Now subtract the numerators (28 − 30 = -2) and keep the common denominator 63 unchanged.
Working: 28 − 30/63 = -2/63

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 2 and 63 is 1, confirming that -2/63 cannot be reduced further—it is already in its simplest irreducible form.
Working: -2/63

Step 5: Decimal & Percentage Representation
Dividing the numerator -2 by denominator 63 produces a repeating decimal (approximately -0.031746, or -3.1746%).
Working: -2 ÷ 63 = -0.031746 (-3.1746%)

Key Values:
- Simplified Fraction: -2/63
- Mixed Number Form: -2/63
- Decimal Value: -0.031746
- Percentage: -3.1746%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-4-9-minus-10-21/
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4/9 − 10/21 = -2/63

Simplified Fraction

-2/63

Mixed Number

Proper (-2/63)

Decimal Value

-0.031746

Percentage

-3.1746%

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Step-by-Step Solution: 4/9 − 10/21

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 4/9 by 7, and multiply the numerator and denominator of 10/21 by 3 so both fractions share the common base 63.

4 × 7/9 × 7 = 28/63 and 10 × 3/21 × 3 = 30/63

Step 3

Subtract the Numerators

Now subtract the numerators (28 − 30 = -2) and keep the common denominator 63 unchanged.

28 − 30/63 = -2/63

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 2 and 63 is 1, confirming that -2/63 cannot be reduced further—it is already in its simplest irreducible form.

-2/63

Step 5

Decimal & Percentage Representation

Dividing the numerator -2 by denominator 63 produces a repeating decimal (approximately -0.031746, or -3.1746%).

-2 ÷ 63 = -0.031746 (-3.1746%)

Visual Representation

The diagram below illustrates 4/9 minus 10/21 visually:

−

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`-2/63`
Mixed Number Form	`-2/63`
Decimal Form	`-0.031746`
Percentage	`-3.1746%`

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Frequently Asked Questions

What is 4/9 minus 10/21 as a fraction?

4/9 − 10/21 in simplest fraction form is -2/63.

What is 4/9 minus 10/21 as a decimal?

4/9 − 10/21 converted to a decimal is -0.031746.

What is 4/9 minus 10/21 as a percentage?

4/9 − 10/21 expressed as a percentage is -3.1746%.

Does 4/9 minus 10/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately -0.031746...) because the denominator contains prime factors other than 2 and 5.