All SAT II Math I Resources
Example Questions
Example Question #3 : Other Mathematical Relationships
varies inversely as the square of and directly as the cube of .
If and , then . Calculate if .
varies inversely as and directly as the cube of . This means that for some constant of variation ,
We can write this relationship alternatively as
where the initial conditions can be substituted on the left side and final conditions, on the right. We will be solving for in the equation
Example Question #71 : Mathematical Relationships
Sarah notices her map has a scale of . She measures between Beaver Falls and Chipmonk Cove. How far apart are the cities?
is the same as
So to find out the distance between the cities
Example Question #1 : Direct Proportionality
If an object is hung on a spring, the elongation of the spring varies directly as the mass of the object. A 20 kg object increases the length of a spring by exactly 7.2 cm. To the nearest tenth of a centimeter, by how much does a 32 kg object increase the length of the same spring?
Let be the mass of the weight and the elongation of the spring. Then for some constant of variation ,
We can find by setting from the first situation:
so
In the second situation, we set and solve for :
which rounds to 11.5 centimeters.
Example Question #72 : Mathematical Relationships
Sunshine paint is made by mixing three parts yellow paint and one part red paint. How many gallons of yellow paint should be mixed with two quarts of red paint?
(1 gallon = 4 quarts)
First set up the proportion:
x =
Then convert this to gallons:
Example Question #73 : Mathematical Relationships
Sally currently has 192 books. Three months ago, she had 160 books. By what percentage did her book collection increase over the past three months?
To find the percentage increase, divide the number of new books by the original amount of books:
She has 32 additional new books; she originally had 160.
Example Question #2 : Direct Proportionality
Find for the proportion .
To find x we need to find the direct proportion. In order to do this we need to cross multiply and divide.
From here we mulitply 100 and 1 together. This gets us 100 and now we divide 100 by 4 which results in
Example Question #74 : Mathematical Relationships
On a map of the United States, Mark notices a scale of . If the distance between New York City and Los Angeles in real life is , how far would the two cities be on Mark's map?
If the real distance between the two cities is , and = , then we can set up the proportional equation:
Example Question #3 : Direct Proportionality
If and , find and .
We cannot solve the first equation until we know at least one of the variables, so let's solve the second equation first to solve for . We therefore get:
With our , we can now find x using the first equation:
We therefore get the correct answer of and .
Example Question #3 : Direct Proportionality
If an object is hung on a spring, the elongation of the spring varies directly with the mass of the object. A 33 kilogram object increases the length of a spring by exactly 6.6 centimeters. To the nearest tenth of a kilogram, how much mass must an object posess to increase the length of that same spring by exactly 10 centimeters?
Let be the mass of the weight and the elongation of the spring, respectively. Then for some constant of variation ,
.
We can find by setting :
Therefore .
Set and solve for :
kilograms
Example Question #2 : How To Find Direct Variation
If is directly proportional to and when at , what is the value of the constant of proportionality?
The general formula for direct proportionality is
where is the proportionality constant. To find the value of this , we plug in and
Solve for by dividing both sides by 12
So .