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If y varies directly as the square root of x and y is 10 when x = 1, find y when...


Question

If y varies directly as the square root of x and y is 10 when x = 1, find y when x = 4.

Options

A) 18

B) 20

C) 30

D) 40

The correct answer is B.

Explanation:

\(y \approx \sqrt{x}\)
\(y = k\sqrt{x}\)
At \(y = 10, x = 1\)
\(10 = k\sqrt{1}\)
\(k = 1\)
\(\rightarrow y = \sqrt{x}\)
At \(x = 4, y = \sqrt{4} = 2\)

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Dicussion (1)

  • \(y \approx \sqrt{x}\)
    \(y = k\sqrt{x}\)
    At \(y = 10, x = 1\)
    \(10 = k\sqrt{1}\)
    \(k = 1\)
    \(\rightarrow y = \sqrt{x}\)
    At \(x = 4, y = \sqrt{4} = 2\)

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