An astronomer collected observations of pulses from an unusual cepheid variable star, and found that from the initial observation of 0.150 seconds for the length of the pulse, the pulse length increased regularly to 0.175, 0.200, .225, . . . , seconds until the last observation of 1.125 seconds, when it ceased pulsing altogether. (a) What was the mean pulse length? (b) how many pulse observations did the astronomer collect? Solution 1.125 = 0.175 + 38*0.025 thus there are 39 readings. mean pulse length = (0.175+1.125)/2 = 0.650 s.