Other Forms of Direct Variation

What type of variation does this scenario represent?

The length of time you charge your cell phone

and the battery power

• direct propotion

• inverse variation

• joint variation

• none of these

Determine if the relationship between the two quantities is a direct variation. Explain your reasoning.

• yes, the constant of variation is 1/2

• yes, the constant of variation is 2

• no, there is constant of variation.

Determine if the relationship between the two quantities is a direct variation. Explain your reasoning.

• yes, the constant of variation is 8.

• no, there is no constant of variation

• yes, the constant of variation is 1/8

Determine if there is a constant of variation. If so, explain what it represents. The equation y = 9.50 x represents the number of dollars y Marty paid for x movie tickets.

• The constant of variation is 9.50. This means that Marty paid $9.50 for each movie ticket

• There is no constant of variation. There is not a direct variation between the number of tickets and the total cost.

The cost of paper varies directly with the number of reams bought. Suppose 2 reams cost $5.10. Write an equation that could be used to find the cost of x reams of paper.

• y= 5.10x

• y=2.55x + 2.55

• y = 2.55x

• 2.55y = x

Recall that the length a spring stretches varies directly with the amount of weight attached to it. A certain spring stretches 5 cm when a 10-gram weight is attached. Write a direct variation equation relating the weight x and the amount of stretch y.

• y = 0.5x

• y= 2x

• y= 5x + 10

• y= 2x +5

Determine if the relationship between the two quantities is a direct variation. Explain your reasoning.

• yes, the constant of variation is 2

• yes, the constant of variation is 1/2

• no, there is no constant of variation

The letter k in the equation y = kx stands for

• the constant of proportionality

• king

• queen

Does this table of values represent a direct variation?

• Yes

• No

Do x and y show direct variation?

y = 5x

• Yes

• No