90 hazelnuts = 125g
Therefore, the mass of one hazelnut is this...
90 / 90 = 125 / 90
1 hazelnut = 25/18 grams
630 calories = 100 grams
100 divided by 25/18 = 72
Therefore...
630 / 72 = 1 hazelnut
AND THE ANSWER IS
8.75 calories = 1 hazelnut
I am setting the week hourly rate to x, and the weekend to y. Here is how the equation is set up:
13x + 14y = $250.90
15x + 8y = $204.70
This is a system of equations, and we can solve it by multiplying the top equation by 4, and the bottom equation by -7. Now it equals:
52x + 56y = $1003.60
-105x - 56y = -$1432.90
Now we add these two equations together to get:
-53x = -$429.30 --> 53x = $429.30 --> (divide both sides by 53) x = 8.10. This is how much she makes per hour on a week day.
Now we can plug in our answer for x to find y. I am going to use the first equation, but you could use either.
$105.30 + 14y = $250.90. Subtract $105.30 from both sides --> 14y = $145.60 divide by 14 --> y = $10.40
Now we know that she makes $8.10 per hour on the week days, and $10.40 per hour on the weekends. Subtracting 8.1 from 10.4, we figure out that she makes $2.30 more per hour on the weekends than week days.
In Cartesian coordinates, the region (call it
) is the set

In the plane
, we have

which is a circle with radius
. Then we can better describe the solid by

so that the volume is

While doable, it's easier to compute the volume in cylindrical coordinates.

Then we can describe
in cylindrical coordinates by

so that the volume is

40 ways. 6!/3!(6-3)! =120. We are only trying to find 3 ways. 120 is the total, 120/30 =40. So 40 is the answer.