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 3/8 + 4/5 + 7/3 + 9/10 = ? Thank you for your assistance. Priscila

Hi Priscila,

You need a common denominator which is some number divisible by 10, 3, 5 and 8. In fact it's most efficient if you find the least such number. I would start by factoring each of the denominators into primes.

10 = 2 × 5
3 = 3
5 = 5
8 = 2 × 2 × 2.

Now build the common denominator from the primes you have found, 2, 3 and 5.

If the common denominator is to be divisible by 10 it must have a 2 and a 5 as prime factors so I begin my construction of this number as

2 × 5

It must also be divisible by 3 so it needs a three. Hence I continue by

2 × 5 × 3.

The next denominator is 5 but 2 × 5 × 3 is already divisible by 5 so I can move to the last denominator,8. To be divisible by 8 the common denominator must contain three twos. It already has one two so it needs two more. Hence my common denominator is

2 × 5 × 3 × 2 × 2 = 120.

Can you complete the problem now?

Write back if you need more help,
Penny

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