Eric Nicholas K's answer to Fortunato's Primary 5 Maths Fractions Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
1965 answers (Tutor Details)
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The terms will cancel each other all the way until 1/9.

After all the cancellations, the surviving terms are 1/1 and -1/10, and of course 1/1 - 1/10 = 9/10.

This method is also known as the method of differences.