What is 1/18 plus 4/21? (Answer: 31/126)

Exact Answer

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Problem: What is 1/18 plus 4/21?
Formula / Expression: 1/18 + 4/21
Final Answer: 31/126
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 18 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 126 (which is smaller than their product 18 × 21 = 378, keeping the calculation simpler).
Working: LCD(18, 21) = 126

Step 2: Convert to Equivalent Fractions with Common Denominator 126
Multiply the numerator and denominator of 1/18 by 7, and multiply the numerator and denominator of 4/21 by 6 so both fractions share the common base 126.
Working: 1 × 7/18 × 7 = 7/126 and 4 × 6/21 × 6 = 24/126

Step 3: Add the Numerators
Now add the numerators (7 + 24 = 31) and keep the common denominator 126 unchanged.
Working: 7 + 24/126 = 31/126

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 31 and 126 is 1, confirming that 31/126 cannot be reduced further—it is already in its simplest irreducible form.
Working: 31/126

Step 5: Decimal & Percentage Representation
Dividing the numerator 31 by denominator 126 produces a repeating decimal (approximately 0.246032, or 24.6032%).
Working: 31 ÷ 126 = 0.246032 (24.6032%)

Key Values:
- Simplified Fraction: 31/126
- Mixed Number Form: 31/126
- Decimal Value: 0.246032
- Percentage: 24.6032%

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Solved with FractionsCalc:
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1/18 + 4/21 = 31/126

Simplified Fraction

31/126

Mixed Number

Proper (31/126)

Decimal Value

0.246032

Percentage

24.6032%

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Step-by-Step Solution: 1/18 + 4/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 18 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 126 (which is smaller than their product 18 × 21 = 378, keeping the calculation simpler).

LCD(18, 21) = 126

Step 2

Convert to Equivalent Fractions with Common Denominator 126

Multiply the numerator and denominator of 1/18 by 7, and multiply the numerator and denominator of 4/21 by 6 so both fractions share the common base 126.

1 × 7/18 × 7 = 7/126 and 4 × 6/21 × 6 = 24/126

Step 3

Add the Numerators

Now add the numerators (7 + 24 = 31) and keep the common denominator 126 unchanged.

7 + 24/126 = 31/126

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 31 and 126 is 1, confirming that 31/126 cannot be reduced further—it is already in its simplest irreducible form.

31/126

Step 5

Decimal & Percentage Representation

Dividing the numerator 31 by denominator 126 produces a repeating decimal (approximately 0.246032, or 24.6032%).

31 ÷ 126 = 0.246032 (24.6032%)

Visual Representation

The diagram below illustrates 1/18 plus 4/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`31/126`
Mixed Number Form	`31/126`
Decimal Form	`0.246032`
Percentage	`24.6032%`

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Frequently Asked Questions

What is 1/18 plus 4/21 as a fraction?

1/18 + 4/21 in simplest fraction form is 31/126.

What is 1/18 plus 4/21 as a decimal?

1/18 + 4/21 converted to a decimal is 0.246032.

What is 1/18 plus 4/21 as a percentage?

1/18 + 4/21 expressed as a percentage is 24.6032%.

Does 1/18 plus 4/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.246032...) because the denominator contains prime factors other than 2 and 5.