# Tutor profile: Matthew G.

## Questions

### Subject: Environmental Engineering

What is the cross-sectional area of a pipe if water flows at a flow rate of 3 (m^3/s) and has a velocity of 1.5 (m/s).

We know Q (flow rate)= V (velocity) * A (cross-sectional area) based on dimensional analysis. By rearranging the equation we can solve for A. 3 (m^3/s) / 1.5 (m/s) = 2 m^2

### Subject: Basic Chemistry

Determine the number of moles of NaCl in 600 grams of NaCl.

We know the following from the periodic table molecular weight of Na= 22.90 grams/mole molecular weight of Cl is 35.45 grams/mole Adding these together we know the molecular weight is 58.35 grams/mole. So, dividing 600 grams by 58.35 grams/mole is 10.28 moles.

### Subject: Algebra

Let x be the price of small popcorn and y be the price of soda at the movies. We know 2 small popcorn and one soda is $10. So 2x + y = $10 We also know 2 small popcorn and two soda is $14. So 2x + 2y = $14 So what is the price of one small popcorn and one soda?

Subtract the second equation by the first as a linear system of equations. 2x+2y = $14 -(2x+y)= $10 ---------------------- y= $4 plugging y=$4 back into the equation: 2x+y= $10 we get 2x = $6. Dividing both sides of the equation by 2 we get x = $3 We now know one small popcorn (x) is $3 and one soda (y) is $4!

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