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Let y varies directly as x. If y=12 when...

Let y varies directly as x. If y=12 when x=4, then write a linear equation. What is value of y when x=5 ?

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Given that, y varies directly as x.
i.e., `y prop x implies y =kx`
Given, y=12 and x=4
12=4k
`implies " " k=(12)/(4)`
`therefore " " k=3`
On putting the value of k in Eq. (i), we get
y=3x
When x=5, then from Eq. (ii), we get
`y=3xx5 implies y=15`
Hence, the value of y is 15.
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