Maths Olympiad Prep

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, 2014

Algebra Difficulty 1.4 Junior Find the answer Canada

If 10x105=100410^x \cdot 10^5 = 100^4, what is the value of xx?

Pick one

Solution

Since 100=102100=10^2, then 1004=(102)4=108100^4 = (10^2)^4 = 10^8.

Therefore, we must solve the equation 10x105=10810^x \cdot 10^5 = 10^8, which is equivalent to 10x+5=10810^{x+5}=10^8.

Thus, x+5=8x+5=8 or x=3x=3.

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.