y is inversely proportional to the square root of x - OCR - GCSE Maths - Question 14 - 2019 - Paper 1

From the information given, when x = 25, y = 7:

$7 = \frac{k}{\sqrt{25}}$

Since (\sqrt{25} = 5), this simplifies to:

$7 = \frac{k}{5}$

Multiplying both sides by 5 gives:

$k = 35$

Now substituting k back into the equation when x = 100:

$y = \frac{35}{\sqrt{100}}$

Since (\sqrt{100} = 10), we have:

$y = \frac{35}{10} = 3.5$

Thus, the value of y when x = 100 is:

3.5