Answer:
The constant of variation in a direct variation is the constant (unchanged) ratio of two variable quantities.
The formula for direct variation is
y=kx (or y=kx )
where k is the constant of variation .
Example 1:
If y varies directly as x and y=15 when x=24 , find x when y=25 .
Find the constant of variation.
k=yx=1524=58y=58x
To find x , substitute 25 for y .
25=58x x=40
The constant of variation in an indirect variation is the constant (unchanged) product between two variable quantities.
The formula for indirect variation is
xy=k (or y=kx )
where k is the constant of variation .
Example 2:
If it takes 4 hours at an average speed of 90 km/h to do a certain journey, how long would it take at 120 km/h?
Find the constant of variation.
k = speed · time
k=90⋅4=360
Then,
time=kspeed =360120 =3 hours
