What is 2/7 minus 10/21? (Answer: -4/21)

Exact Answer

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Problem: What is 2/7 minus 10/21?
Formula / Expression: 2/7 − 10/21
Final Answer: -4/21
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
Notice that 21 is an exact multiple of 7 (7 × 3 = 21). The Least Common Denominator (LCD) is simply 21, meaning we only need to scale one fraction.
Working: LCD(7, 21) = 21

Step 2: Convert to Equivalent Fractions with Common Denominator 21
Multiply the numerator and denominator of 2/7 by 3, and multiply the numerator and denominator of 10/21 by 1 so both fractions share the common base 21.
Working: 2 × 3/7 × 3 = 6/21 and 10 × 1/21 × 1 = 10/21

Step 3: Subtract the Numerators
Now subtract the numerators (6 − 10 = -4) and keep the common denominator 21 unchanged.
Working: 6 − 10/21 = -4/21

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 4 and 21 is 1, confirming that -4/21 cannot be reduced further—it is already in its simplest irreducible form.
Working: -4/21

Step 5: Decimal & Percentage Representation
Dividing the numerator -4 by denominator 21 produces a repeating decimal (approximately -0.190476, or -19.0476%).
Working: -4 ÷ 21 = -0.190476 (-19.0476%)

Key Values:
- Simplified Fraction: -4/21
- Mixed Number Form: -4/21
- Decimal Value: -0.190476
- Percentage: -19.0476%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-2-7-minus-10-21/
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2/7 − 10/21 = -4/21

Simplified Fraction

-4/21

Mixed Number

Proper (-4/21)

Decimal Value

-0.190476

Percentage

-19.0476%

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Step-by-Step Solution: 2/7 − 10/21

Step 1

Find the Least Common Denominator (LCD)

Notice that 21 is an exact multiple of 7 (7 × 3 = 21). The Least Common Denominator (LCD) is simply 21, meaning we only need to scale one fraction.

LCD(7, 21) = 21

Step 2

Convert to Equivalent Fractions with Common Denominator 21

Multiply the numerator and denominator of 2/7 by 3, and multiply the numerator and denominator of 10/21 by 1 so both fractions share the common base 21.

2 × 3/7 × 3 = 6/21 and 10 × 1/21 × 1 = 10/21

Step 3

Subtract the Numerators

Now subtract the numerators (6 − 10 = -4) and keep the common denominator 21 unchanged.

6 − 10/21 = -4/21

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 4 and 21 is 1, confirming that -4/21 cannot be reduced further—it is already in its simplest irreducible form.

-4/21

Step 5

Decimal & Percentage Representation

Dividing the numerator -4 by denominator 21 produces a repeating decimal (approximately -0.190476, or -19.0476%).

-4 ÷ 21 = -0.190476 (-19.0476%)

Visual Representation

The diagram below illustrates 2/7 minus 10/21 visually:

−

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`-4/21`
Mixed Number Form	`-4/21`
Decimal Form	`-0.190476`
Percentage	`-19.0476%`

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Frequently Asked Questions

What is 2/7 minus 10/21 as a fraction?

2/7 − 10/21 in simplest fraction form is -4/21.

What is 2/7 minus 10/21 as a decimal?

2/7 − 10/21 converted to a decimal is -0.190476.

What is 2/7 minus 10/21 as a percentage?

2/7 − 10/21 expressed as a percentage is -19.0476%.

Does 2/7 minus 10/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately -0.190476...) because the denominator contains prime factors other than 2 and 5.