Example 3, No. 7 & 9

a) Speed = distance (m) / time (s)
       = 0.9 / 1.69
       = 0.533 (3 s.f.)

b) The time taken for a repetition of the wave is longer when the tension is low; the time taken for a repetition of the wave is shorter when the tension is high. Therefore, the speed of the wave is directly proportionate to the amount of tension.