exponenets
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Source: Beat The GMAT — Problem Solving |
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musicdaemon
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Stuart@KaplanGMAT
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5^15 * 4^8 = 2×10^nvinviper1 wrote:5*15×4*8=2×10*n
* = exponent
What is n?
1. 6
2. 7
3. 8
4. 15
5. 23
5^15 * (2*2)^8 = 2×10^n
5^15 * 2^16 = 2×10^n
5^15 * 2^15 * 2 = 2×10^n
(5*2)^15 * 2 = 2×10^n
10^15 * 2 = 2×10^n
10^15 = 10^n
15 = n
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4 is a perfect square and can be expressed as 2^2 ... so all you are doing is replacing the 4 with the 2^2.vinviper1 wrote:4^8 = (2*2)^8 = 2^16
Is this a general exponent rule?
Doesn't work with others like 5s
Or 9^2 = (3*3)^2 = 3^4
Thanks!
9^2 => we know 9 is a perfect square ... so 9 can be written as 3^2.
So 9^2 => (3^2)^2 = 3^4.
