A frequency distribution of pulse rates of patients is given below. The frequency of the modal class and that of the succeeding class are not known.
Class interval (beats/min): 40–45 45–50 50–55 55–60 60–65
Frequency: 9 8 x(x−6) 4
If the mode of the distribution is 47.5 beats per minute, calculate the value of x (the frequency of the modal class).
(a) 10
(b) 15
(c) 14
(d) 12