The heights of a group of 1000 women are normall distributed. The mean height of the group is 170 cm with a standard deviation of 10 cm. What is the best approximation of the number of women between 170 cm and 180 cm tall?
1) 950
2) 680
3) 340
4) 170
1) 950
2) 680
3) 340
4) 170