Aim: How do we solve coin problems?

 
Homework: Complete handout sheet

Lesson Review:
Remember that the number of coins times the value of each coin in cents, is = total value of the coins in cents.

Example:
Bill has 4 times as many quarters as dimes. In all he has $2.20. How many coins of each type does she have?

Solution:
Let x= number of dimes (x is always = to the coin in the problems that follows the word "than" or "as") then, 4x is = to the number of quarters

The value of a dime is 10 cents and the value of a quarter is 25 cents
The total value of all the coins is $2.20 cents which is the same as 220 cents after we multiply $2.20 times 100 cents.

Now we write the equation: Dimes + Quarters = $2.20
x + 4x = $2.20 Now I can't add a dime and a quarter without converting then to cents, so:
(10)x + 25(4x) = $2.20 (100)
1 0 x + 100x = 220
110x= 220
x= 2 , so there are 2 dimes.
Therefore 4x quarters is 4(2) which = 8 quarters.
Practice Exercises:
http://mathforum.org/dr.math/faq/faq.coins.html
http://www.purplemath.com/modules/coinprob.htm
http://www.onlinemathlearning.com/coin-problems.html