Danielle Scribe Post Chapter 3 Section 3.1

Today in class we went over 2 test problems that no one got right and we also went over some of section 3.1.
2 Test Problems
#11. John has 20 ounces of a 20% of salt solution, How much salt should he add to make it a 25% solution?

concentration= 20%=.20
amount= 20 ounces =20
added= x

Equation for solving problem #11 :
(.20)20 + 1x = .25(20+x)
4 + x = 5 + .25 x
.75x = 1
x= 1/.75
x=4/3 oz.

#12. A tank has a capacity of 10 gallons. When it is full, it contains 15% alcohol. How many gallons must be replaced by an 80% alcohol solution to give 10 gallons of 70% solution?

Equation for solving #12 :
1.5 -. 15x + .80x  = 7
After solving this equation you should get
x=8.46 gallons

Next we went over some of Section 3.1, mainly interval notation
and set notation

example of interval notation
x  > -1

example of set notation
( -1, infinity symbol)

We did a problem in class to help us distinguish interval notation from set notation

4x-5 > 13
      +5        +5
4x/4 > 18/4 

x> 9/2
interval notaion

[9/2 , infinity symbol]
set notation    

the next scribe :Ifeanyi