What is 1/4 plus 3/5? (Answer: 17/20)

Exact Answer

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Problem: What is 1/4 plus 3/5?
Formula / Expression: 1/4 + 3/5
Final Answer: 17/20
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 4 and 5 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 4 × 5 = 20.
Working: LCD(4, 5) = 20

Step 2: Convert to Equivalent Fractions with Common Denominator 20
Multiply the numerator and denominator of 1/4 by 5, and multiply the numerator and denominator of 3/5 by 4 so both fractions share the common base 20.
Working: 1 × 5/4 × 5 = 5/20 and 3 × 4/5 × 4 = 12/20

Step 3: Add the Numerators
Now add the numerators (5 + 12 = 17) and keep the common denominator 20 unchanged.
Working: 5 + 12/20 = 17/20

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 17 and 20 is 1, confirming that 17/20 cannot be reduced further—it is already in its simplest irreducible form.
Working: 17/20

Step 5: Decimal & Percentage Representation
Dividing the numerator 17 by denominator 20 yields an exact terminating decimal of 0.85 (or 85%).
Working: 17 ÷ 20 = 0.85 (85%)

Key Values:
- Simplified Fraction: 17/20
- Mixed Number Form: 17/20
- Decimal Value: 0.85
- Percentage: 85%

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1/4 + 3/5 = 17/20

Simplified Fraction

17/20

Mixed Number

Proper (17/20)

Decimal Value

0.85

Percentage

85%

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Step-by-Step Solution: 1/4 + 3/5

Step 1

Find the Least Common Denominator (LCD)

The denominators 4 and 5 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 4 × 5 = 20.

LCD(4, 5) = 20

Step 2

Convert to Equivalent Fractions with Common Denominator 20

Multiply the numerator and denominator of 1/4 by 5, and multiply the numerator and denominator of 3/5 by 4 so both fractions share the common base 20.

1 × 5/4 × 5 = 5/20 and 3 × 4/5 × 4 = 12/20

Step 3

Add the Numerators

Now add the numerators (5 + 12 = 17) and keep the common denominator 20 unchanged.

5 + 12/20 = 17/20

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 17 and 20 is 1, confirming that 17/20 cannot be reduced further—it is already in its simplest irreducible form.

17/20

Step 5

Decimal & Percentage Representation

Dividing the numerator 17 by denominator 20 yields an exact terminating decimal of 0.85 (or 85%).

17 ÷ 20 = 0.85 (85%)

Visual Representation

The diagram below illustrates 1/4 plus 3/5 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`17/20`
Mixed Number Form	`17/20`
Decimal Form	`0.85`
Percentage	`85%`

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Frequently Asked Questions

What is 1/4 plus 3/5 as a fraction?

1/4 + 3/5 in simplest fraction form is 17/20.

What is 1/4 plus 3/5 as a decimal?

1/4 + 3/5 converted to a decimal is 0.85.

What is 1/4 plus 3/5 as a percentage?

1/4 + 3/5 expressed as a percentage is 85%.

Does 1/4 plus 3/5 result in a terminating or repeating decimal?

It results in an exact terminating decimal (0.85) because the denominator in simplest terms contains only prime factors 2 and/or 5.