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Pre-Algebra Videos 217 videos
Who wants to be a millionaire? In this video, learn about compound interest, interest rates, and the compound interest formula. You'll be buying th...
ACT Math: Pre-Algebra Drill 5, Problem 2. If a and b are prime numbers, how many factors does ab have?
SAT Math 4.3 Numbers and Operations 2174 Views
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SAT Math 4.3 Numbers and Operations
SAT Math 4.3 Numbers and Operations
Transcript
- 00:02
Getting' Shmoopy with it...
- 00:04
If a and b are different prime numbers, which
- 00:06
of the following could also be prime?
- 00:08
And here are the potential answers...
- 00:13
The best way to deal with these questions
Full Transcript
- 00:15
is to substitute real prime numbers for the variables.
- 00:20
Let's say a = 2 and b = 3.
- 00:24
Now we can test each answer choice.
- 00:27
Choice A: 2 times 3 is 6. 6 is not prime. Boom -- gone.
- 00:32
Choice B: 2 cubed is 8. 8 isn't prime. Outta here.
- 00:37
Choice C: 2 plus 3 is 5. 5 is prime.
- 00:42
Choice D: 3 squared is 9. 9 isn't prime.
- 00:46
Only choice C can give us a prime number... ...so that's our answer.
- 00:57
An answer choice by any other letter would smell as sweet...
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