Problem of the Day At a concession stand, hamburgers are selling at a rate of 160 hamburgers per hour. The table shows the rate at which wraps are selling. Minutes 1 2 3 4 Wraps Sold 2.5 5 7.5 10 Concession Sales a. Do hamburgers or wraps sell faster? Explain. b. Graph equations that represent the growth rates of hamburgers sold and wraps sold in the same coordinate plane. Compare the steepness of the graphs. What does this mean in the context of the problem? Items Sold Minutes

Proportional Relationships Also called the constant of proportionality A.K.A Direct Variation When a straight line goes through (0,0), it has a proportional relationship Origin The constant of variation is _______________ The slope Also called the constant of proportionality y = constant x (y=kx) The equation looks like ___________________

Proportional Relationships The slope is ____________________ The rate of change Constant ____________ Equation _____________ Using k, write a proportion to find y when x = 24

Is this a proportional relationship? CoCo Puffs Marsh-mallows General Mills is coming out with a new cereal called Hot Cocoa. They experimented with some samples to decide their recipe. We will chart to samples. What is the CONSTANT? How do you know? 240 342 What would the equation be?

Or check if the values form a proportion Identifying Direct Variation You need two things Or check if the values form a proportion Constant SLOPE Origin (0,0)

If four Oreo cookies contain 220 calories If four Oreo cookies contain 220 calories. How many calories would be consumed if you eat three? Find the constant variation first.     Write and use the equation to solve for three cookies.

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Is this a proportional relationship? Explain your answer Gallons of gas used Miles driven 2 56 3 84 4 100 5 128 6 154 Is this a proportional relationship? Explain your answer