The incubation time for Rhode Island Red chicks is normally distributed 27 days and standard deviation of approximately 3 days. If 1000 eggs are incubated, how many chicks do we expect will hatch in 27 to 33 days?

68% probability lies between 2 standard deviations from the mean of a standard normal distribution. This goes both ways from 0. 27 to 33 is +2 from the mean so we assume .68/2 = 34% should be the probability of hatching. The expected amount should be $p \left(x\right) x = 1000 \cdot .34 = 340$