The duration of routine operations at Chicago General Hospital has approximately a normal distribution with an average of 130 minutes and a standard deviation of 12 minutes. What proportion of operations lasted between 90 and 135 minutes?
.
a. 0.85
b. 0.79
c. 0.80
d. 0.66

D) 0.66

Step-by-step explanation:

P(90<X<135) = normalcdf(90,135,130,12) = 0.6611097268 ≈ 0.66

So the proportion of operations that lasted between 90 and 135 minutes is 0.66

50 min

step-by-step explanation:

they will be decreasing both their times in half

60 / 2 = 30

40/2 = 20

30 + 20 = 50