Well 5 + 4 is 9, and so if the girls are 5 in the ratio, the fraction would be 5/9. I hope this helps!
a. Let 
be a random variable representing the weight of a ball bearing selected at random. We're told that 
, so
where 
. This probability is approximately
b. Let 
be a random variable representing the weight of the 
-th ball that is selected, and let 
be the mean of these 4 weights,
The sum of normally distributed random variables is a random variable that also follows a normal distribution,
so that
Then
c. Same as (b).
Set up the equation of two ratios:
3 racks 36 racks
----------- = --------------
15 min x
Solve this for x: 3x =540; x = 180 minutes, or 3 hours
Answer: True
One angle of a right triangle = 90°
Let x = the acute angle of one angle.
Let y = the angle of the other angle.
Because the sum of angles in a triangle is 180°,
x + y + 90 = 180
x + y = 90
y = 90 - x
Therefore the angles for each of the two triangles are
x, 90° - x, 90°.
The two triangles are therefore similar because of AAA (Angle, Angle, Angle).
