What is 7/45 plus 8/21? (Answer: 169/315)

Exact Answer

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Problem: What is 7/45 plus 8/21?
Formula / Expression: 7/45 + 8/21
Final Answer: 169/315
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Step-by-Step Solution:

Step 1: Find the Least Common Denominator (LCD)
The denominators 45 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 315 (which is smaller than their product 45 × 21 = 945, keeping the calculation simpler).
Working: LCD(45, 21) = 315

Step 2: Convert to Equivalent Fractions with Common Denominator 315
Multiply the numerator and denominator of 7/45 by 7, and multiply the numerator and denominator of 8/21 by 15 so both fractions share the common base 315.
Working: 7 × 7/45 × 7 = 49/315 and 8 × 15/21 × 15 = 120/315

Step 3: Add the Numerators
Now add the numerators (49 + 120 = 169) and keep the common denominator 315 unchanged.
Working: 49 + 120/315 = 169/315

Step 4: Check if the Fraction Can Be Simplified
The Greatest Common Divisor (GCD) of 169 and 315 is 1, confirming that 169/315 cannot be reduced further—it is already in its simplest irreducible form.
Working: 169/315

Step 5: Decimal & Percentage Representation
Dividing the numerator 169 by denominator 315 produces a repeating decimal (approximately 0.536508, or 53.6508%).
Working: 169 ÷ 315 = 0.536508 (53.6508%)

Key Values:
- Simplified Fraction: 169/315
- Mixed Number Form: 169/315
- Decimal Value: 0.536508
- Percentage: 53.6508%

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Solved with FractionsCalc:
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7/45 + 8/21 = 169/315

Simplified Fraction

169/315

Mixed Number

Proper (169/315)

Decimal Value

0.536508

Percentage

53.6508%

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Step-by-Step Solution: 7/45 + 8/21

Step 1

Find the Least Common Denominator (LCD)

The denominators 45 and 21 share a common factor (GCD = 3). Finding their Least Common Multiple gives an LCD of 315 (which is smaller than their product 45 × 21 = 945, keeping the calculation simpler).

LCD(45, 21) = 315

Step 2

Convert to Equivalent Fractions with Common Denominator 315

Multiply the numerator and denominator of 7/45 by 7, and multiply the numerator and denominator of 8/21 by 15 so both fractions share the common base 315.

7 × 7/45 × 7 = 49/315 and 8 × 15/21 × 15 = 120/315

Step 3

Add the Numerators

Now add the numerators (49 + 120 = 169) and keep the common denominator 315 unchanged.

49 + 120/315 = 169/315

Step 4

Check if the Fraction Can Be Simplified

The Greatest Common Divisor (GCD) of 169 and 315 is 1, confirming that 169/315 cannot be reduced further—it is already in its simplest irreducible form.

169/315

Step 5

Decimal & Percentage Representation

Dividing the numerator 169 by denominator 315 produces a repeating decimal (approximately 0.536508, or 53.6508%).

169 ÷ 315 = 0.536508 (53.6508%)

Visual Representation

The diagram below illustrates 7/45 plus 8/21 visually:

Summary & Alternative Representations

Property / Format	Value
Lowest Terms Fraction	`169/315`
Mixed Number Form	`169/315`
Decimal Form	`0.536508`
Percentage	`53.6508%`

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Frequently Asked Questions

What is 7/45 plus 8/21 as a fraction?

7/45 + 8/21 in simplest fraction form is 169/315.

What is 7/45 plus 8/21 as a decimal?

7/45 + 8/21 converted to a decimal is 0.536508.

What is 7/45 plus 8/21 as a percentage?

7/45 + 8/21 expressed as a percentage is 53.6508%.

Does 7/45 plus 8/21 result in a terminating or repeating decimal?

It results in a repeating decimal (approximately 0.536508...) because the denominator contains prime factors other than 2 and 5.