All SAT II Math I Resources
Example Questions
Example Question #2 : How To Find Inverse Variation
varies inversely as the square of . If , then . Find if (nearest tenth, if applicable).
The variation equation is for some constant of variation .
Substitute the numbers from the first scenario to find :
The equation is now .
If , then
Example Question #3 : How To Find Inverse Variation
The current, in amperes, that a battery provides an electrical object is inversely proportional to the resistance, in ohms, of the object.
A battery provides 1.2 amperes of current to a flashlight whose resistance is measured at 20 ohms. How much current will the same battery supply to a flashlight whose resistance is measured at 16 ohms?
If is the current and is the resistance, then we can write the variation equation for some constant of variation :
or, alternatively,
To find , substitute :
The equation is . Now substitute and solve for :
Example Question #32 : Proportionalities
The volume of a fixed mass of gas varies inversely as the atmospheric pressure, as measured in millibars, acting on it, and directly as the temperature, as measured in kelvins, acting on it.
A balloon is filled to a capacity of exactly 100 cubic meters at a time at which the temperature is 310 kelvins and the atmospheric pressure is 1,020 millibars. The balloon is released, and an hour later, the balloon is subject to a pressure of 900 millibars and a temperature of 290 kelvins. To the nearest cubic meter, what is the new volume of the balloon?
If are the volume, pressure, and temperature, then the variation equation will be, for some constant of variation ,
To calculate , substitute :
The variation equation is
so substitute and solve for .
Example Question #4 : How To Find Inverse Variation
If is inversely proportional to and knowing that when , determine the proportionality constant.
The general formula for inverse proportionality for this problem is
Given that when , we can find by plugging them into the formula.
Solve for by multiplying both sides by 5
So .
Example Question #101 : Mathematical Relationships
The number of days needed to construct a house is inversely proportional to the number of people that help build the house. It took 28 days to build a house with 7 people. A second house is being built and it needs to be finished in 14 days. How many people are needed to make this happen?
The general formula of inverse proportionality for this problem is
where is the number of days, is the proportionality constant, and is number of people.
Before finding the number of people needed to build the house in 14 days, we need to find . Given that the house can be built in 28 days with 7 people, we have
Multiply both sides by 7 to find .
So . Thus,
Now we can find the how many people are needed to build the house in 14 days.
Solve for . First, multiply by on both sides:
Divide both sides by 14
So it will take 14 people to complete the house in 14 days.
Example Question #41 : Proportionalities
The number of days to construct a house varies inversely with the number of people constructing that house. If it takes 28 days to construct a house with 6 people helping out, how long will it take if 20 people are helping out?
The statement, 'The number of days to construct a house varies inversely with the number of people constructing that house' has the mathematical relationship , where D is the number of days, P is the number of people, and k is the variation constant. Given that the house can be completed in 28 days with 6 people, the k-value is calculated.
This k-value can be used to find out how many days it takes to construct a house with 20 people (P = 20).
So it will take 8.4 days to build a house with 20 people.
Example Question #103 : Mathematical Relationships
The speed of a turtle is indirectly proportional to its weight in pounds. At 10 pounds, the turtle's speed was 0.5. What is the speed of the turtle if it grew and weigh 50 pounds?
Write the formula for the indirect proportional relationship. If one variable increases, the other variable must also decrease.
Using speed and weight as and respectively, the equation becomes:
Use the initial condition of the turtle's speed and weight to solve for the constant.
Substitute this value back into the formula. The formula becomes:
We want to know the speed of the turtle when it is 50 pounds. Divide the variable on both sides to isolate the speed variable.
Substitute the new weight of the turtle.
Example Question #41 : Other Mathematical Relationships
x varies inversely with y. When x=10, y=6. When x=3, what is y?
Inverse variation takes the form:
Plugging in:
Then solve when x=3:
Example Question #42 : Other Mathematical Relationships
The rate of speed is indirectly proportional to the time it takes to travel somewhere. If a person walks at a rate of 3 miles per hour and it takes them 4 hours to get to their destination how far did they travel?
For an indirect proportionality, use the equation
If rate of speed is indirectly proportional to the time, then the speed is y (3 miles per hour) and the time is x (4 hours).
Replace those into the indirect proportionality formula
Solve for k by multiplying by 4 on both sides
The person traveled 12 miles.
Example Question #151 : Sat Subject Test In Math I
Evaluate .
The system has no solution.
The system has no solution.
Rewrite the two equations by setting and and substituting:
In terms of and , this is the system of linear equations:
Solve the first equation for :
Substitute this expression for in the second equation, then simplify:
The statement is identically false. Therefore, the original system cannot have a solution.
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