What is 21/63 + 3/8?
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Here's how we add
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Step 1Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term. So, we multiply 21 by 8, and get 168, then we multiply 63 by 8 and get 504. Now for the second term. You multiply 3 by 63, and get 189, then multiply 63 by 8 and get 504. We now have a new problem, that looks like this:
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Step 2Since our denominators match, we can add the numerators. 168 + 189 = 357 That gives us the sum, which is
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Step 3Now, do we need to simplify this fraction? First, we attempt to divide it by 2... No good. So next you try the next prime number, which is 3... Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:
So far so good... let's try to divide by that number again. No good. So next you try the next prime number, which is 5... No good. So next you try the next prime number, which is 7... Are both the numerator and the denominator evenly divisible by 7? Yes! So we reduce it:
So far so good... let's try to divide by that number again. No good. So next you try the next prime number, which is 11... No good. So next you try the next prime number, which is 13... No good. So next you try the next prime number, which is 17... No good. So next you try the next prime number, which is 19... No good. 19 is larger than 17. So we're done reducing. And we're done! Here's the final answer to 21/63 + 3/8
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