What is 8/51 plus 7/21? (Answer: 25/51)

Exact Answer

==================================================
Problem: What is 8/51 plus 7/21?
Formula / Expression: 8/51 + 7/21
Final Answer: 25/51
==================================================

Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 51 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 357 (which is smaller than their product 51 × 21 = 1071, keeping the calculation simpler).
Working: LCD(51, 21) = 357

Step 2: Convert to Equivalent Fractions with Common Denominator 357
Multiply the numerator and denominator of 8/51 by 7, and multiply the numerator and denominator of 7/21 by 17 so both fractions share the common base 357.
Working: 8 × 7/51 × 7 = 56/357 and 7 × 17/21 × 17 = 119/357

Step 3: Add the Numerators
Now add the numerators (56 + 119 = 175) and keep the common denominator 357 unchanged.
Working: 56 + 119/357 = 175/357

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 175 and 357, which is 7. Divide both the numerator and denominator by 7.
Working: 175 ÷ 7/357 ÷ 7 = 25/51

Step 5: Decimal & Percentage Representation
Dividing the numerator 25 by denominator 51 produces a repeating decimal (approximately 0.490196, or 49.0196%).
Working: 25 ÷ 51 = 0.490196 (49.0196%)

Key Values:
- Simplified Fraction: 25/51
- Mixed Number Form: 25/51
- Decimal Value: 0.490196
- Percentage: 49.0196%

--------------------------------------------------
Solved with FractionsCalc:
https://fractionscalc.com/what-is-8-51-plus-7-21/
==================================================

8/51 + 7/21 = 25/51

Simplified Fraction

25/51

Mixed Number

Proper (25/51)

Decimal Value

0.490196

Percentage

49.0196%

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: 8/51 + 7/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 51 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 357 (which is smaller than their product 51 × 21 = 1071, keeping the calculation simpler).

LCD(51, 21) = 357

Step 2

Convert to Equivalent Fractions with Common Denominator 357

Multiply the numerator and denominator of 8/51 by 7, and multiply the numerator and denominator of 7/21 by 17 so both fractions share the common base 357.

8 × 7/51 × 7 = 56/357 and 7 × 17/21 × 17 = 119/357

Step 3

Add the Numerators

Now add the numerators (56 + 119 = 175) and keep the common denominator 357 unchanged.

56 + 119/357 = 175/357

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 175 and 357, which is 7. Divide both the numerator and denominator by 7.

175 ÷ 7/357 ÷ 7 = 25/51

Step 5

Decimal & Percentage Representation

Dividing the numerator 25 by denominator 51 produces a repeating decimal (approximately 0.490196, or 49.0196%).

25 ÷ 51 = 0.490196 (49.0196%)

Visual Representation

The diagram below illustrates 8/51 plus 7/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`25/51`
Mixed Number Form	`25/51`
Decimal Form	`0.490196`
Percentage	`49.0196%`

Was this solution helpful?

Help us improve our free step-by-step tools

Frequently Asked Questions

What is 8/51 plus 7/21 as a fraction?

8/51 + 7/21 in simplest fraction form is 25/51.

What is 8/51 plus 7/21 as a decimal?

8/51 + 7/21 converted to a decimal is 0.490196.

What is 8/51 plus 7/21 as a percentage?

8/51 + 7/21 expressed as a percentage is 49.0196%.

Does 8/51 plus 7/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.490196...) because the denominator contains prime factors other than 2 and 5.