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a is directly proportional to b. When a = 8, b = 6.

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Retired Moderator
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a is directly proportional to b. When a = 8, b = 6. [#permalink]

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09 Jan 2010, 13:04
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a is directly proportional to b. When a = 8, b = 6.

c is inversely proportional to b. When c = –12, b = –3.

If a = 12, what is the value of c?

Isn't C =36?
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09 Jan 2010, 14:00
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$$a$$ is directly proportional to $$b$$ --> $$a=kb$$ --> $$a=8$$, $$b=6$$ --> $$8=6k$$ --> $$k=\frac{4}{3}$$;

$$c$$ is inversely proportional to $$b$$ --> $$c=\frac{n}{b}$$ --> $$c=-12$$, $$b =-3$$ --> $$-12=\frac{n}{-3}$$ --> $$n=36$$;

$$a=12$$ --> $$b=\frac{a}{k}=\frac{12}{\frac{4}{3}}=9$$ --> $$c=\frac{n}{b}=\frac{36}{9}=4$$.
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11 Jan 2010, 08:04
Thanks for the explanation. Correct answer is 4.
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Re: a is directly proportional to b. When a = 8, b = 6. [#permalink]

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12 Sep 2017, 03:44
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Re: a is directly proportional to b. When a = 8, b = 6.   [#permalink] 12 Sep 2017, 03:44
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