Do Now:Use elimination. 1.

2. The sum of two numbers is 20. Their difference is 4. Find the numbers.

Answer: 12 and 8

2 8

3

x y

x y

(11/3, 2/3)

More Elimination Method

Coordinate Algebra

Standard: A.REI.6

Essential Question

How do I solve a system of equations using the ELIMINATION method?

Ex. 1) Use Elimination

Answer: (-1, 4)

4 3 8

3 5 23

x y

x y

Ex. 2) Use Elimination

Answer: (2, 1)

3 5 11

2 3 7

x y

x y

Bonus Example:

3 6

3 2 2 9

3 1

x y z

x y z

y z

(-1, 2, -1)

Assignment:

Do Now: Solve each system using any method you

choose. 1. y = 5x

x + 2y = 22 2. 2y – x = -5

4y – 3x = -1

(2, 10)

(-9, -7)

WORD Problems EQ

How do I solve word problems using systems of equations?

Coin Word Problems

Formula:

(price1)(amount1) + (price2)(amount2) + etc.

= Total $$$$$

Quarter price is: 0.25Dime price is: 0.10Nickel price is: 0.05Penny price is: 0.01

Ex 1)

Sam has $2.05 in quarters and dimes. He has four more quarters than dimes. How many does he have of each coin?

Answer: 3 dimes & 7 quarters

Ex 2)

A kindergarten class collected $3.50 in nickels and dimes for the American Red Cross. In all they collected 45 coins. How many of each did they collect?

Answer: 20 nickels & 25 dimes

Age Word Problems

For age word problems, you simply translate.

Remember, “less than” and “subtracted from” statements get reversed when you write their expressions. Also, “Younger than!”

Ex 3)

Suzy is 8 years younger than her sister Madeline. If the sum of their ages is 32, how old are they?

Answer: Madeline is 20 yrs. old & Suzy is 12 yrs. old

Ex. 4)

Eight more than twice Joe’s age is 9 years less than 3 times his age. How old is he?

Answer: Joe is 17 years old