Algebra 1 25 Oct 20111) Put papers from your group folder into your binder.2) Put your binder, hw and text on your desk.

CHECK YOUR HOMEWORKCHECK YOUR HOMEWORK √ √ or X your answersor X your answers

Warm-up: silentlyWarm-up: silentlyA Starbucks coffee costs 230 rubles in Moscow, Russia.

Convert to dollars if $1 = 31 rubles

finished? do Improving your visual thinking skills pg. 113

Objective

Students will summarize direct variation and explore inverse variation relationships.

Students will take notes and use think-pair-share.

Homework due todayvarious assignments

ONE “free ticket”

Homework due next classpg. 128 +: 5, 13, 14

debrief currency conversions

3) write a sentence telling someone how to find the cost of your object in another currency4) Find an EQUATION5) Is the relationship directly proportional?How do you know?6) What if you knew the cost of your object in another country’s currency. How would you convert to $$?

Direct variation: An equation in the form of y = kx or k = is a direct variation. The quantities represented by x and y are directly proportional and k is the constant of

variation.

If one quantity increases, so does the other. If cost in dollars increases, so does cost in pesos.If one quantity decreases, so does the other. The shorter the trip, the less time it takes.

hours ↑ pay ↑ miles ↓ time ↓

yx

We can use an equation to solve direct variation problems

If x is distance in inches y is the distance in cm, THEN y = 2.54x #cm=

Find the # of cm using the equation if:1) x = 14 inches2) x = 0.8 inches3) x = 36 inches

2.54( )( )1 1cm xinches

inch

Inverse Variation

Try opening a door by pushing close to the hinge. As the distance from the hinge INCREASES the

amount of force needed to open the door DECREASES.

distance ↑ force↓

notes…An equation in the form is an inverse variation. Quantities represented by x and y are inversely

proportional and k is the constant of variation.

Note– if xy is a constant for every (x,y) pair (the same number) in a table, it is an indirect variation…

kyx

OR k = xy

page 128, #6Look at each table- how can we decide if it is a

direct variation, inverse variation or neither?

DIRECT VARIATION y = kx or k =

INVERSE VARIATION y = or k = yxk = yx

#6. Do (a) together- GRAPH the relationship then check k= y/x and k = yx for each

yx

kx

debrief

what did you learn today?

What was easy? What is still difficult?