What is 3/4 plus 4/5? (Answer: 31/20)

Exact Answer

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Problem: What is 3/4 plus 4/5?
Formula / Expression: 3/4 + 4/5
Final Answer: 1 11/20 (31/20)
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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 3/4 by 5, and multiply the numerator and denominator of 4/5 by 4 so both fractions share the common base 20.
Working: 3 × 5/4 × 5 = 15/20 and 4 × 4/5 × 4 = 16/20

Step 3: Add the Numerators
Now add the numerators (15 + 16 = 31) and keep the common denominator 20 unchanged.
Working: 15 + 16/20 = 31/20

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 31 and 20 is 1, confirming that 31/20 cannot be reduced further—it is already in its simplest irreducible form.
Working: 31/20

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (31) is greater than the denominator (20), divide 31 by 20: it goes in 1 whole time(s) with a remainder of 11, giving the mixed number 1 11/20.
Working: 31/20 = 1 11/20

Step 6: Decimal & Percentage Representation
Dividing the numerator 31 by denominator 20 yields an exact terminating decimal of 1.55 (or 155%).
Working: 31 ÷ 20 = 1.55 (155%)

Key Values:
- Simplified Fraction: 31/20
- Mixed Number Form: 1 11/20
- Decimal Value: 1.55
- Percentage: 155%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-3-4-plus-4-5/
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3/4 + 4/5 = 31/20

Simplified Fraction

31/20

Mixed Number

1 11/20

Decimal Value

1.55

Percentage

155%

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

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

3 × 5/4 × 5 = 15/20 and 4 × 4/5 × 4 = 16/20

Step 3

Add the Numerators

Now add the numerators (15 + 16 = 31) and keep the common denominator 20 unchanged.

15 + 16/20 = 31/20

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 31 and 20 is 1, confirming that 31/20 cannot be reduced further—it is already in its simplest irreducible form.

31/20

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (31) is greater than the denominator (20), divide 31 by 20: it goes in 1 whole time(s) with a remainder of 11, giving the mixed number 1 11/20.

31/20 = 111/20

Step 6

Decimal & Percentage Representation

Dividing the numerator 31 by denominator 20 yields an exact terminating decimal of 1.55 (or 155%).

31 ÷ 20 = 1.55 (155%)

Visual Representation

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

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`31/20`
Mixed Number Form	`1 11/20`
Decimal Form	`1.55`
Percentage	`155%`

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Frequently Asked Questions

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

3/4 + 4/5 in simplest fraction form is 31/20 (or 1 11/20 as a mixed number).

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

3/4 + 4/5 converted to a decimal is 1.55.

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

3/4 + 4/5 expressed as a percentage is 155%.

How do you write 3/4 plus 4/5 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 31/20 can be written as the mixed number 1 11/20.

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

It results in an exact terminating decimal (1.55) because the denominator in simplest terms contains only prime factors 2 and/or 5.