What is 11/60 plus 9/21? (Answer: 257/420)

Exact Answer

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Problem: What is 11/60 plus 9/21?
Formula / Expression: 11/60 + 9/21
Final Answer: 257/420
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 60 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 420 (which is smaller than their product 60 × 21 = 1260, keeping the calculation simpler).
Working: LCD(60, 21) = 420

Step 2: Convert to Equivalent Fractions with Common Denominator 420
Multiply the numerator and denominator of 11/60 by 7, and multiply the numerator and denominator of 9/21 by 20 so both fractions share the common base 420.
Working: 11 × 7/60 × 7 = 77/420 and 9 × 20/21 × 20 = 180/420

Step 3: Add the Numerators
Now add the numerators (77 + 180 = 257) and keep the common denominator 420 unchanged.
Working: 77 + 180/420 = 257/420

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 257 and 420 is 1, confirming that 257/420 cannot be reduced further—it is already in its simplest irreducible form.
Working: 257/420

Step 5: Decimal & Percentage Representation
Dividing the numerator 257 by denominator 420 produces a repeating decimal (approximately 0.611905, or 61.1905%).
Working: 257 ÷ 420 = 0.611905 (61.1905%)

Key Values:
- Simplified Fraction: 257/420
- Mixed Number Form: 257/420
- Decimal Value: 0.611905
- Percentage: 61.1905%

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Solved with FractionsCalc:
https://fractionscalc.com/what-is-11-60-plus-9-21/
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11/60 + 9/21 = 257/420

Simplified Fraction

257/420

Mixed Number

Proper (257/420)

Decimal Value

0.611905

Percentage

61.1905%

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Step-by-Step Solution: 11/60 + 9/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 60 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 420 (which is smaller than their product 60 × 21 = 1260, keeping the calculation simpler).

LCD(60, 21) = 420

Step 2

Convert to Equivalent Fractions with Common Denominator 420

Multiply the numerator and denominator of 11/60 by 7, and multiply the numerator and denominator of 9/21 by 20 so both fractions share the common base 420.

11 × 7/60 × 7 = 77/420 and 9 × 20/21 × 20 = 180/420

Step 3

Add the Numerators

Now add the numerators (77 + 180 = 257) and keep the common denominator 420 unchanged.

77 + 180/420 = 257/420

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 257 and 420 is 1, confirming that 257/420 cannot be reduced further—it is already in its simplest irreducible form.

257/420

Step 5

Decimal & Percentage Representation

Dividing the numerator 257 by denominator 420 produces a repeating decimal (approximately 0.611905, or 61.1905%).

257 ÷ 420 = 0.611905 (61.1905%)

Visual Representation

The diagram below illustrates 11/60 plus 9/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`257/420`
Mixed Number Form	`257/420`
Decimal Form	`0.611905`
Percentage	`61.1905%`

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Frequently Asked Questions

What is 11/60 plus 9/21 as a fraction?

11/60 + 9/21 in simplest fraction form is 257/420.

What is 11/60 plus 9/21 as a decimal?

11/60 + 9/21 converted to a decimal is 0.611905.

What is 11/60 plus 9/21 as a percentage?

11/60 + 9/21 expressed as a percentage is 61.1905%.

Does 11/60 plus 9/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.611905...) because the denominator contains prime factors other than 2 and 5.