Question
Find the fourth proportional to 3, 12, 15
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Answer
$\begin{aligned} & \text { Let fourth proportional to } \\ & 3,12,15 \text { be } x \\ & \text { then } 3: 12:: 15: x \\ & \Rightarrow 3 \times x=12 \times 15 \\ & x=\frac{12 \times 15}{3} \\ & =60\end{aligned}$
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