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).
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