October 01, 2013
Lesson 3.5
Investment and Mixture
The simple interest formula: I = prt
When we focus on situations involving one year
we do not need to include t.
Page 225 #18
Daudi invests a certain amount of money in an account that has
an APR of 2.5%. He invests $400 more than that amount in a
3.5% APR account. If the total annual interest from the
investments is $242, how much was invested in each account?
Account
Principal
first
n
2.5%
second
n+400
3.5%
Interest Rate Annual Interest
.025n
.035(n+400)
Equation:
Solution:
1
October 01, 2013
Page 226 #38
A solution of gasoline and oil used for a gas-powered
weed trimmer is 8% oil. How much gasoline must be
added to 3 gallons of the solution to obtain a new
solution that is 5% oil?
Solution
Volume
of solution
Percent of
pure ingredient
Volume of
pure ingredient
original
3 gallons
8%
.08(3)
new
3+x gallons
5%
.05(3+x)
The volume of pure ingredient will remain the same!
Equation:
Solution:
Answer statement:
1.8 gallons of gasoline must be added.
2
October 01, 2013
Accounts
Amount
Rate
Interest
3
October 01, 2013
Solution
Volume
of solution
Percent of
pure ingredient
Volume of
pure ingredient
4