The museum of science in boston has an exhibit in which metal balls drop down a chute, bounce around, and wind up in one of 21 bins. after 1000 balls have dropped, the heights within the bins clearly follow a bell-shaped curve. the standard deviation is 3 bins.
about how many balls are in bins 1 through 17?
a) 500
b) 680
c) 950
d) 975