:1. Solution. Since (420-500)/100 = -80/100 = -.8 and
(525-500)/100 = 25/100 = .25, the percentage scoring between 420
and 525 is equal to the area under the normal curve between -.8
and .25. The area between -.8 and 0 is about 58/2 = 29%, and
the area between 0 and .25 is about 20/10 = 10%. So the answer
is 29% + 10% = 39%, which is closest to 40%.