The mean score of a college entrance test is 500; the standard deviation is 75. the scores are normally distributed. what percent of the students scored below 320?

To find the percentage of students who scored below 320 we proceed as follows:
σ=75
μ=500
the z-score of this information is given by:
z=(x-μ)/σ
thus the z-score when x=320 will be:
z=(320-500)/75
z=-2.4
thus:
P(x<320)=P(z=-2.4)=0.0082~0.82%
Thus:
0.82%

10 2/15 hours

Step-by-step explanation:

If we have a candle that is 11 2/5 inches tall

It burns 1 1/8 inches per hour.  We need to divide to see how long the candle will last

11 2/5 ÷ 1 1/8

I will convert the mixed numbers to improper fractions

11 2/5 = (5*11+2)/5 = 57/5

1 1/8 = (8*1+1)/8 = 9/8

57/5 ÷ 9/8

Copy dot flip

57/5 * 8/9

456/45

Now we change it back to a mixed number

45 goes into 456  10 times with 6 left over

10 6/45

This simplifies to 10 2/15