Problem 1
<h3>Answer: 20</h3>
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Explanation:
The factors of 20 are 1,2,4,5,10,20
They are numbers that pair up to multiply to 20. For instance, 5*4 = 20. We only focus on whole numbers.
In the list given to us, we see that only 20 is a factor of 20. Something like 17 is not a factor of 20, and so on for the other values.
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Problem 2
<h3>Answer: 21</h3>
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Explanation:
List out the multiples of 3 to get {3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...}
The stuff in bold are values found in the original list.
Now list out the multiples of 7 to get {7, 14, 21, 28, 35, 42, ...}
We can see that only 21 is found in both lists of multiples we wrote out.
Note how 3*7 = 21, which is not a coincidence.
