What is 7/42 plus 15/21? (Answer: 37/42)

Exact Answer

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Problem: What is 7/42 plus 15/21?
Formula / Expression: 7/42 + 15/21
Final Answer: 37/42
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
Notice that 42 is an exact multiple of 21 (21 × 2 = 42). The Least Common Denominator (LCD) is simply 42, meaning we only need to scale one fraction.
Working: LCD(42, 21) = 42

Step 2: Convert to Equivalent Fractions with Common Denominator 42
Multiply the numerator and denominator of 7/42 by 1, and multiply the numerator and denominator of 15/21 by 2 so both fractions share the common base 42.
Working: 7 × 1/42 × 1 = 7/42 and 15 × 2/21 × 2 = 30/42

Step 3: Add the Numerators
Now add the numerators (7 + 30 = 37) and keep the common denominator 42 unchanged.
Working: 7 + 30/42 = 37/42

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 37 and 42 is 1, confirming that 37/42 cannot be reduced further—it is already in its simplest irreducible form.
Working: 37/42

Step 5: Decimal & Percentage Representation
Dividing the numerator 37 by denominator 42 produces a repeating decimal (approximately 0.880952, or 88.0952%).
Working: 37 ÷ 42 = 0.880952 (88.0952%)

Key Values:
- Simplified Fraction: 37/42
- Mixed Number Form: 37/42
- Decimal Value: 0.880952
- Percentage: 88.0952%

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Solved with FractionsCalc:
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7/42 + 15/21 = 37/42

Simplified Fraction

37/42

Mixed Number

Proper (37/42)

Decimal Value

0.880952

Percentage

88.0952%

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Step-by-Step Solution: 7/42 + 15/21

Step 1

Find the Least Common Denominator (LCD)

Notice that 42 is an exact multiple of 21 (21 × 2 = 42). The Least Common Denominator (LCD) is simply 42, meaning we only need to scale one fraction.

LCD(42, 21) = 42

Step 2

Convert to Equivalent Fractions with Common Denominator 42

Multiply the numerator and denominator of 7/42 by 1, and multiply the numerator and denominator of 15/21 by 2 so both fractions share the common base 42.

7 × 1/42 × 1 = 7/42 and 15 × 2/21 × 2 = 30/42

Step 3

Add the Numerators

Now add the numerators (7 + 30 = 37) and keep the common denominator 42 unchanged.

7 + 30/42 = 37/42

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 37 and 42 is 1, confirming that 37/42 cannot be reduced further—it is already in its simplest irreducible form.

37/42

Step 5

Decimal & Percentage Representation

Dividing the numerator 37 by denominator 42 produces a repeating decimal (approximately 0.880952, or 88.0952%).

37 ÷ 42 = 0.880952 (88.0952%)

Visual Representation

The diagram below illustrates 7/42 plus 15/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`37/42`
Mixed Number Form	`37/42`
Decimal Form	`0.880952`
Percentage	`88.0952%`

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Frequently Asked Questions

What is 7/42 plus 15/21 as a fraction?

7/42 + 15/21 in simplest fraction form is 37/42.

What is 7/42 plus 15/21 as a decimal?

7/42 + 15/21 converted to a decimal is 0.880952.

What is 7/42 plus 15/21 as a percentage?

7/42 + 15/21 expressed as a percentage is 88.0952%.

Does 7/42 plus 15/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.880952...) because the denominator contains prime factors other than 2 and 5.