What is 8/9 plus 9/10? (Answer: 161/90)

Exact Answer

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Problem: What is 8/9 plus 9/10?
Formula / Expression: 8/9 + 9/10
Final Answer: 1 71/90 (161/90)
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 9 and 10 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 9 × 10 = 90.
Working: LCD(9, 10) = 90

Step 2: Convert to Equivalent Fractions with Common Denominator 90
Multiply the numerator and denominator of 8/9 by 10, and multiply the numerator and denominator of 9/10 by 9 so both fractions share the common base 90.
Working: 8 × 10/9 × 10 = 80/90 and 9 × 9/10 × 9 = 81/90

Step 3: Add the Numerators
Now add the numerators (80 + 81 = 161) and keep the common denominator 90 unchanged.
Working: 80 + 81/90 = 161/90

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 161 and 90 is 1, confirming that 161/90 cannot be reduced further—it is already in its simplest irreducible form.
Working: 161/90

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (161) is greater than the denominator (90), divide 161 by 90: it goes in 1 whole time(s) with a remainder of 71, giving the mixed number 1 71/90.
Working: 161/90 = 1 71/90

Step 6: Decimal & Percentage Representation
Dividing the numerator 161 by denominator 90 produces a repeating decimal (approximately 1.788889, or 178.8889%).
Working: 161 ÷ 90 = 1.788889 (178.8889%)

Key Values:
- Simplified Fraction: 161/90
- Mixed Number Form: 1 71/90
- Decimal Value: 1.788889
- Percentage: 178.8889%

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Solved with FractionsCalc:
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8/9 + 9/10 = 161/90

Simplified Fraction

161/90

Mixed Number

1 71/90

Decimal Value

1.788889

Percentage

178.8889%

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Step-by-Step Solution: 8/9 + 9/10

Step 1

Find the Least Common Denominator (LCD)

The denominators 9 and 10 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 9 × 10 = 90.

LCD(9, 10) = 90

Step 2

Convert to Equivalent Fractions with Common Denominator 90

Multiply the numerator and denominator of 8/9 by 10, and multiply the numerator and denominator of 9/10 by 9 so both fractions share the common base 90.

8 × 10/9 × 10 = 80/90 and 9 × 9/10 × 9 = 81/90

Step 3

Add the Numerators

Now add the numerators (80 + 81 = 161) and keep the common denominator 90 unchanged.

80 + 81/90 = 161/90

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 161 and 90 is 1, confirming that 161/90 cannot be reduced further—it is already in its simplest irreducible form.

161/90

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (161) is greater than the denominator (90), divide 161 by 90: it goes in 1 whole time(s) with a remainder of 71, giving the mixed number 1 71/90.

161/90 = 171/90

Step 6

Decimal & Percentage Representation

Dividing the numerator 161 by denominator 90 produces a repeating decimal (approximately 1.788889, or 178.8889%).

161 ÷ 90 = 1.788889 (178.8889%)

Visual Representation

The diagram below illustrates 8/9 plus 9/10 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`161/90`
Mixed Number Form	`1 71/90`
Decimal Form	`1.788889`
Percentage	`178.8889%`

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Frequently Asked Questions

What is 8/9 plus 9/10 as a fraction?

8/9 + 9/10 in simplest fraction form is 161/90 (or 1 71/90 as a mixed number).

What is 8/9 plus 9/10 as a decimal?

8/9 + 9/10 converted to a decimal is 1.788889.

What is 8/9 plus 9/10 as a percentage?

8/9 + 9/10 expressed as a percentage is 178.8889%.

How do you write 8/9 plus 9/10 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 161/90 can be written as the mixed number 1 71/90.

Does 8/9 plus 9/10 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.788889...) because the denominator contains prime factors other than 2 and 5.