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FractionsArithmeticElementary schoolabout 0:47

Calculate 9/12 + 9/8: animated lesson

A narrated, step-by-step fractions video lesson with captions. Final answer: 15/8.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.3 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
9/12 + 9/8
2. Step by step
1. $\frac{3}{4} + \frac{9}{8} = \frac{6}{8} + \frac{9}{8}$
  Rewrite both fractions with the least common denominator
2. $\frac{6 + 9}{8} = \frac{15}{8}$
  Add the numerators and keep the denominator
3. $\frac{15}{8} = 1\tfrac{7}{8}$
  Final answer in lowest terms
3. The answer
$\frac{15}{8}$
9/12 + 9/8 = 15/8
4. Check
- Decimal check: 15/8 ≈ 1.875
- As a mixed number: 1 7/8

Transcript

The problem. Here is the problem: 9 over 12 plus 9 over 8. Exact arithmetic with fractions (results kept in lowest terms).

Step by step. Rewrite both fractions with the least common denominator. The LCD of 4 and 8 is 8. Add the numerators and keep the denominator. Final answer in lowest terms.

The answer. So the answer is 15 over 8. Fractions are combined over a common denominator for addition and subtraction, multiplied straight across, and divided by multiplying by the reciprocal. The result is reduced by the greatest common factor.

Check. Decimal check: 15 over 8 approximately 1.875. As a mixed number: 1 7 over 8.

About fractions

Add, subtract, multiply and divide fractions, finding common denominators and simplifying the result.

Calculate 9/12 + 9/8: Fractions Step-by-Step Lesson