Direct Proportional

The cost, c, of a circular table is directly proportional to the square of the radius, r. A circular table with a radius of 40cm cost £50. What is the cost of a circular table with a radius of 60cm?

H varies directly to the cube of c. When H = 40, c = 2. Find the value of c when H = 5000.

C is directly proportional to the square root of y. When C = 12.8, y = 16. Find C when y = 400.

Which situation represents a proportional relationship?

Select the correct answer ○ in each row.

A family makes homemade pickles. They pick the pickles at a rate of 80 pickles per 5 jars. Which answer choices best represent packing y pickles in x jars at that rate? Select TWO correct answers.

Answer the following questions.

c

d

g

i

f

y=4500x

100

no

10

yes

4500

y = 1500x

1,500

10,500

y=10x

The table is​ ​ (a)   , because it ​ (b)   a constant ratio.

If so, what is the constant of proportionality?​ (c)  

• non-proportional

• proportional

• does not have

• has

• no constant

• k=14

Answer explanation

A proportional relationship means that two quantities maintain a constant ratio. In this case, the relationship does not exhibit a constant ratio, hence the answer is No.

A recipe for pastry requires 180g of sugar to make 540g of pastry. How many grams of sugar will be needed to make 5400g of pastry?