Answer:
Step-by-step explanation:

Let

denote the number of minutes spent brushing his teeth, and let

be the mean and

the standard deviation for this distribution.

The z-score corresponding to this probability is approximately

, which means

Next, (note the sign change)

The corresponding z-score is approximately

, so you have

Solving the two equations for

and

, you'll find that the mean is approximately

and the standard deviation is approximately

.
Answer:
1.25 g
Step-by-step explanation:
you start with 20g at 0 seconds.
divide by half after 2 seconds and you have 10g.
at 4 seconds you have 5g.
at 6 seconds you have 2.5g.
at 8 seconds you have 1.25g.
Cos ø = Base/ Hypotenuse
Cos 30 = y/32
Root 3/2 = y/32
y= 16root3
X= 16