Direct Inverse Jointly Variations

Which of the following variations has the product of two quantities as the constant?

(45 seconds)

• direct variation

• inverse variation

• joint variation

• combined variation

What do you call a variation when more than one type of variation occurs in the same equation?

(45 seconds)

• direct variation

• inverse variation

• joint variation

• combined variation

The amount of paint (p) needed to paint the walls of a room varies directly as the area (A) of the wall. If 2 gallons of paint is needed to paint a 40 m² wall, how many gallons of paint are needed to paint a wall with an area of 100 m²?

Answer: ___ gallons

(5 MINUTES)

(PROBLEM SOLVING:INVERSE) Two college students decided to rent an apartment near the school where they are studying. The nearest and cheapest apartment costs is P 5,000 a month, which they find too much for their monthly budget. How many students WILL THEY NEED to share the rent so that each will pay only P 1,250 a month? (Final answer only: Pattern: ____students) (3 points)

(5 MINUTES)

Using the table of values for inverse variation, what is the equation of variation?

• y = -40x

Suppose y varies directly as x.
If  y = 22.5 when x = 15, find y when x = 20.

• 1.5

• 337.5

• 30

• 16.875

If y varies directly as x and inversely as z, and y = 24 when x = 48 and z = 4, find x when y = 44 and z = 6.

• 126

• 132

• 148

• 154

What type of variation does this scenario represent?
The grade you earn in a class
and the number of assignments you complete
and the number of hours you study

• direct variation

• inverse variation

• joint variation

• none of these

Suppose y varies jointly as x & z. 
If y = -180 when z = 15
and x = -3,
then find y when x = 7 and z = -5.

• -140

• 140

• -4

• 4

Suppose y varies inversely with x.
If y = 150 when x = 2, find y when x = 25.

• 300

• 75

• 1,875

• 12