Proportion Things to remember: Start by checking the question for squares, cubes and roots; is directly proportional to y” looks like x y or x = ky “x α is inversely proportional to y” looks like x or x = “x α Questions: 1. 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. ........................................................... (3) (b) Hence, or otherwise, calculate the value of when = 4 S f S = ........................................................... (1) (Total 4 marks) 2. In a factory, chemical reactions are carried out in spherical containers. The time, T minutes, the chemical reaction takes is directly proportional to the square of the radius, R cm, of the spherical container. When R = 120, T = 32 Find the value of T when R = 150 T = ........................................................... (Total 4 marks) 3. d is directly proportional to the square of t.
Proportion Things to remember: Start by checking the question for squares, cubes and roots; “x is directly proportional to y” looks like x α y or x = ky “x is inversely proportional to y” looks like x α or x = Questions: 1. 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. ........................................................... (3) (b) Hence, or otherwise, calculate the value of S when f = 4 S = ........................................................... (1) (Total 4 marks) 2. In a factory, chemical reactions are carried out in spherical containers. The time, T minutes, the chemical reaction takes is directly proportional to the square of the radius, R cm, of the spherical container. When R = 120, T = 32 Find the value of T when R = 150 T = ........................................................... (Total 4 marks) 3. d is directly proportional to the square of t.
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