Thread: Year 10 GCSE Paper question varies inversely as the square

The shutter speed, S, of a camera varies inversely as the square of the aperture setting, f.

When f= 8, S= 125

a) find a formula for S in terms of f.



b) Hence, or otherwise calculate the value of S when f= 4

thanks for any time anybody spends on this question

Rob

If x varies inversely to y, then:

Where k is the constant value for any values of (x,y).

If x varies inversely to the square of y, then:



Find the constant, and then replace in the equation:


Use this equation to find (b).