What is 10/25 plus 15/21? (Answer: 39/35)

Exact Answer

==================================================
Problem: What is 10/25 plus 15/21?
Formula / Expression: 10/25 + 15/21
Final Answer: 1 4/35 (39/35)
==================================================

Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 25 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 25 × 21 = 525.
Working: LCD(25, 21) = 525

Step 2: Convert to Equivalent Fractions with Common Denominator 525
Multiply the numerator and denominator of 10/25 by 21, and multiply the numerator and denominator of 15/21 by 25 so both fractions share the common base 525.
Working: 10 × 21/25 × 21 = 210/525 and 15 × 25/21 × 25 = 375/525

Step 3: Add the Numerators
Now add the numerators (210 + 375 = 585) and keep the common denominator 525 unchanged.
Working: 210 + 375/525 = 585/525

Step 4: Simplify the Fraction to Lowest Terms
Find the Greatest Common Divisor (GCD) of 585 and 525, which is 15. Divide both the numerator and denominator by 15.
Working: 585 ÷ 15/525 ÷ 15 = 39/35

Step 5: Convert Improper Fraction to a Mixed Number
Since the numerator (39) is greater than the denominator (35), divide 39 by 35: it goes in 1 whole time(s) with a remainder of 4, giving the mixed number 1 4/35.
Working: 39/35 = 1 4/35

Step 6: Decimal & Percentage Representation
Dividing the numerator 39 by denominator 35 produces a repeating decimal (approximately 1.114286, or 111.4286%).
Working: 39 ÷ 35 = 1.114286 (111.4286%)

Key Values:
- Simplified Fraction: 39/35
- Mixed Number Form: 1 4/35
- Decimal Value: 1.114286
- Percentage: 111.4286%

--------------------------------------------------
Solved with FractionsCalc:
https://fractionscalc.com/what-is-10-25-plus-15-21/
==================================================

10/25 + 15/21 = 39/35

Simplified Fraction

39/35

Mixed Number

1 4/35

Decimal Value

1.114286

Percentage

111.4286%

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: 10/25 + 15/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 25 and 21 are coprime (they share no common factors other than 1). Therefore, their Least Common Denominator (LCD) is simply their direct product: 25 × 21 = 525.

LCD(25, 21) = 525

Step 2

Convert to Equivalent Fractions with Common Denominator 525

Multiply the numerator and denominator of 10/25 by 21, and multiply the numerator and denominator of 15/21 by 25 so both fractions share the common base 525.

10 × 21/25 × 21 = 210/525 and 15 × 25/21 × 25 = 375/525

Step 3

Add the Numerators

Now add the numerators (210 + 375 = 585) and keep the common denominator 525 unchanged.

210 + 375/525 = 585/525

Step 4

Simplify the Fraction to Lowest Terms

Find the Greatest Common Divisor (GCD) of 585 and 525, which is 15. Divide both the numerator and denominator by 15.

585 ÷ 15/525 ÷ 15 = 39/35

Step 5

Convert Improper Fraction to a Mixed Number

Since the numerator (39) is greater than the denominator (35), divide 39 by 35: it goes in 1 whole time(s) with a remainder of 4, giving the mixed number 1 4/35.

39/35 = 14/35

Step 6

Decimal & Percentage Representation

Dividing the numerator 39 by denominator 35 produces a repeating decimal (approximately 1.114286, or 111.4286%).

39 ÷ 35 = 1.114286 (111.4286%)

Visual Representation

The diagram below illustrates 10/25 plus 15/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`39/35`
Mixed Number Form	`1 4/35`
Decimal Form	`1.114286`
Percentage	`111.4286%`

Was this solution helpful?

Help us improve our free step-by-step tools

Frequently Asked Questions

What is 10/25 plus 15/21 as a fraction?

10/25 + 15/21 in simplest fraction form is 39/35 (or 1 4/35 as a mixed number).

What is 10/25 plus 15/21 as a decimal?

10/25 + 15/21 converted to a decimal is 1.114286.

What is 10/25 plus 15/21 as a percentage?

10/25 + 15/21 expressed as a percentage is 111.4286%.

How do you write 10/25 plus 15/21 as a mixed number?

Because the numerator is greater than the denominator, the improper fraction 39/35 can be written as the mixed number 1 4/35.

Does 10/25 plus 15/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 1.114286...) because the denominator contains prime factors other than 2 and 5.