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Question
If x and y vary inversely as other and x = 5 when y = 15, find x when y = 12 .
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Solution
\[ \text{ Since x and y vary inversely, we have: } \]
\[xy = k\]
\[ \text{ For x = 5 and y = 15, we have: } \]
\[5 \times 15 = k\]
\[ \Rightarrow k = 75\]
\[\text{ For y = 12, we have: } \]
\[12x = 75\]
\[ \Rightarrow x = \frac{75}{12}\]
\[ = \frac{25}{4}\]
\[ \therefore x = \frac{25}{4}\]
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