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This is a typical question a student at any Business School have to deal with during the test. Could you please give me insight on how to solve it. What area of study should I invest in?

A student has obtained an average of 47% across the seven subjects that he has taken so far.

When he takes his eighth and final subject what mark must he obtain to ensure that his overall mark is 50%?

I apologize if the question below has the wrong tag.

roland
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    His total percentage on the seven subjects taken so far must be $7\times 47%=329%$. He needs his total percentage after the 8th paper to be $8\times 50%=400%$, so me must get at least $71%$ on the final paper. To answer your question, I need to know what part of that seems hard to you? – almagest Apr 15 '16 at 11:42

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Initially we have $$\frac{x_1+x_2+\dots+x_7}{7}=0.47$$ Which implies that $$x_1+x_2+\dots+x_7=7\times 0.47=3.29$$ Therefore $$\frac{x_1+x_2+\dots+x_8}{8}=0.50$$ $$\frac{3.29+x_8}{8}=0.50$$ $$3.29+x_8=8\times 0.50$$ $$3.29+x_8=4$$ $$x_8=4-3.29=0.71$$ As far as what you should study to solve this, I'd say the arithmetic mean, algebra and of course percentages.

k170
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