The document discusses direct proportionality, where it states that if one quantity increases, the other also increases, and if one decreases, the other decreases. It provides examples of direct proportional relationships using the formula A = kB, where k is the constant of variation. It shows working through examples of finding the values of one variable when given the other and the proportionality constant k.

2. For two quantities, x and y, an
increase in x causes an increase
in y as well. Similarly, a decrease
in x cause a decrease in y. Uses
keywords like “directly
proportional” or “varies directly”

3. “A varies directly as B”.
A = kB

4. “A varies directly as B”. If A
is 12 when B is 3, what is
the constant variation?
k = 4 A = 4B

5. “A varies directly as B”. If A
is 12 when B is 3, find A
when B is 10.
k = 4 A = 40

6. “X varies directly as Y”. If X
is 10 when Y is 2, find the
X when y = 4
k = 5 X = 20

7. “O is directly proportional
as P”. If O is 40 when P is
4, find O when P is 6.
k = 10 O = 60

8. “D varies directly as E”. If D
is 30 when E is 2, find D
when E is 20
k = 15 D = 300