What is 17/30 plus 12/21? (Answer: 239/210)

Exact Answer

==================================================
Problem: What is 17/30 plus 12/21?
Formula / Expression: 17/30 + 12/21
Final Answer: 1 29/210 (239/210)
==================================================

Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).
Working: LCD(30, 21) = 210

Step 2: Convert to Equivalent Fractions with Common Denominator 210
Multiply the numerator and denominator of 17/30 by 7, and multiply the numerator and denominator of 12/21 by 10 so both fractions share the common base 210.
Working: 17 × 7/30 × 7 = 119/210 and 12 × 10/21 × 10 = 120/210

Step 3: Add the Numerators
Now add the numerators (119 + 120 = 239) and keep the common denominator 210 unchanged.
Working: 119 + 120/210 = 239/210

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 239 and 210 is 1, confirming that 239/210 cannot be reduced further—it is already in its simplest irreducible form.
Working: 239/210

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (239) is greater than the denominator (210), divide 239 by 210: it goes in 1 whole time(s) with a remainder of 29, giving the mixed number 1 29/210.
Working: 239/210 = 1 29/210

Step 6: Decimal & Percentage Representation
Dividing the numerator 239 by denominator 210 produces a repeating decimal (approximately 1.138095, or 113.8095%).
Working: 239 ÷ 210 = 1.138095 (113.8095%)

Key Values:
- Simplified Fraction: 239/210
- Mixed Number Form: 1 29/210
- Decimal Value: 1.138095
- Percentage: 113.8095%

--------------------------------------------------
Solved with FractionsCalc:
https://fractionscalc.com/what-is-17-30-plus-12-21/
==================================================

17/30 + 12/21 = 239/210

Simplified Fraction

239/210

Mixed Number

1 29/210

Decimal Value

1.138095

Percentage

113.8095%

Reduce / Convert Fraction:

Convert Fraction:

Enter Decimal Number:

Enter Percentage: %

What is % of

From Value: To Value:

Simplify Ratio: :

Switch to Proportion / Missing X Solver (A/B = C/D) →

Enter 3 known numbers and leave 1 empty (or type x) to solve:

← Switch to Ratio Simplifier (A:B)

Provide any 2 values below to calculate the remaining:

Price before discount

Discount

Price after discount

You saved

+ Add Sales Tax & Extra Coupon (Optional)

Sales Tax: % Extra Off: %

Provide any 2 values below to calculate the remaining:

Cost

Markup

REVENUE

Gross Profit

Profit Margin

Bill Subtotal

Tip Percentage

Split (People)

👥

Quick Tip:

Total Bill

Split Between

👥

Tip % (Optional)

Include Tip:

Total Price

Quantity

Unit of Measure

← Discount & Sales Tax • Ratio Simplifier (A:B) →

First Number: Second Number:

Find All Factors of:

Dividend: ÷ Divisor:

Number to Round: To Nearest:

Method: Standard (5+ ↑) Always Up (Ceil) Always Down (Floor)

Presets:

√ Square Root of: OR Power (x^y): ^{^}

x² + x + = 0

Number (n! & log):

Circle Radius (r):

Side a: Side b:

Angle (Degrees): °

Numbers (comma separated):

Total Items (n): Choose (r):

Decimal Number:

Number (1–3999):

Step-by-Step Solution: 17/30 + 12/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 30 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 210 (which is smaller than their product 30 × 21 = 630, keeping the calculation simpler).

LCD(30, 21) = 210

Step 2

Convert to Equivalent Fractions with Common Denominator 210

Multiply the numerator and denominator of 17/30 by 7, and multiply the numerator and denominator of 12/21 by 10 so both fractions share the common base 210.

17 × 7/30 × 7 = 119/210 and 12 × 10/21 × 10 = 120/210

Step 3

Add the Numerators

Now add the numerators (119 + 120 = 239) and keep the common denominator 210 unchanged.

119 + 120/210 = 239/210

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 239 and 210 is 1, confirming that 239/210 cannot be reduced further—it is already in its simplest irreducible form.

239/210

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (239) is greater than the denominator (210), divide 239 by 210: it goes in 1 whole time(s) with a remainder of 29, giving the mixed number 1 29/210.

239/210 = 129/210

Step 6

Decimal & Percentage Representation

Dividing the numerator 239 by denominator 210 produces a repeating decimal (approximately 1.138095, or 113.8095%).

239 ÷ 210 = 1.138095 (113.8095%)

Visual Representation

The diagram below illustrates 17/30 plus 12/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`239/210`
Mixed Number Form	`1 29/210`
Decimal Form	`1.138095`
Percentage	`113.8095%`

Was this solution helpful?

Help us improve our free step-by-step tools

Frequently Asked Questions

What is 17/30 plus 12/21 as a fraction?

17/30 + 12/21 in simplest fraction form is 239/210 (or 1 29/210 as a mixed number).

What is 17/30 plus 12/21 as a decimal?

17/30 + 12/21 converted to a decimal is 1.138095.

What is 17/30 plus 12/21 as a percentage?

17/30 + 12/21 expressed as a percentage is 113.8095%.

How do you write 17/30 plus 12/21 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 239/210 can be written as the mixed number 1 29/210.

Does 17/30 plus 12/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.138095...) because the denominator contains prime factors other than 2 and 5.