What is 3/7 minus 9/21? (Answer: 0)

Exact Answer

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Problem: What is 3/7 minus 9/21?
Formula / Expression: 3/7 − 9/21
Final Answer: 0
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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 3/7 by 3, and multiply the numerator and denominator of 9/21 by 1 so both fractions share the common base 21.
Working: 3 × 3/7 × 3 = 9/21 and 9 × 1/21 × 1 = 9/21

Step 3: Subtract the Numerators
Now subtract the numerators (9 − 9 = 0) and keep the common denominator 21 unchanged.
Working: 9 − 9/21 = 0/21

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 0 and 21 is 1, confirming that 0/1 cannot be reduced further—it is already in its simplest irreducible form.

Step 5: Decimal & Percentage Representation
Dividing the numerator 0 by denominator 1 yields an exact terminating decimal of 0 (or 0%).
Working: 0 ÷ 1 = 0 (0%)

Key Values:
- Decimal Value: 0
- Percentage: 0%

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3/7 − 9/21 = 0

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Step-by-Step Solution: 3/7 − 9/21

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 3/7 by 3, and multiply the numerator and denominator of 9/21 by 1 so both fractions share the common base 21.

3 × 3/7 × 3 = 9/21 and 9 × 1/21 × 1 = 9/21

Step 3

Subtract the Numerators

Now subtract the numerators (9 − 9 = 0) and keep the common denominator 21 unchanged.

9 − 9/21 = 0/21

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 0 and 21 is 1, confirming that 0/1 cannot be reduced further—it is already in its simplest irreducible form.

Step 5

Decimal & Percentage Representation

Dividing the numerator 0 by denominator 1 yields an exact terminating decimal of 0 (or 0%).

0 ÷ 1 = 0 (0%)

Visual Representation

The diagram below illustrates 3/7 minus 9/21 visually:

−

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`0`
Mixed Number Form	`0`
Decimal Form	`0`
Percentage	`0%`

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Frequently Asked Questions

What is 3/7 minus 9/21 as a fraction?

3/7 − 9/21 in simplest fraction form is 0.

What is 3/7 minus 9/21 as a decimal?

3/7 − 9/21 converted to a decimal is 0.

What is 3/7 minus 9/21 as a percentage?

3/7 − 9/21 expressed as a percentage is 0%.

Is the answer to 3/7 minus 9/21 a whole number?

Yes, 3/7 − 9/21 simplifies completely to the whole number 0 with no remaining fractional part.