All SAT Math Resources
Example Questions
Example Question #3 : Systems Of Equations
If 8x – 9 is 10 less than 5, what is the value of 4x?
4
1/2
1
2
1/4
2
The first thing to do is to write an algebrai equation for the problem:
8x – 9 = 5 – 10
8x – 9 = –5
8x = 4
x = 1/2
Thus, 4 * x = 2
Example Question #3 : Systems Of Equations
4x - 5y = 12
6y - 3x = -6
Quantity A: x + y
Quantity B: 6
The two quantities are equal
Quantity A is greater
The relationship cannot be determined from the information given
Quantity B is greater
The two quantities are equal
Add the two equations:
4x - 5y = 12 plus
6y - 3x = -6:
4x - 5y + (6y - 3x) = 12 + (-6)
4x - 3x + 6y - 5y = 12 - 6
x + y = 6
Example Question #1 : How To Find The Solution For A System Of Equations
- A charity organization is signing up volunteers to prepare for a fundraiser. Each volunteer can either help setup tables or auction galleries. A volunteer can setup 6 tables per hour or 2 auction galleries per hour. There are 180 tables to be setup as well as 12 auction galleries. If the volunteers will have 3 hours to prepare, how many volunteers must be signed up?
Find out how much a volunteer can produce in 3 hours.
6 tables/hour * 3 hours = 18 tables/hour
180 table need to be setup. If one volunteer can setup 18 in 3 hours, then 10 volunteers will take care of the 180 tables.
2 auction galleries/hour * 3 hours = 6 galleries/hour
2 volunteers will be able to complete 12 auction galleries
10 + 2 = 12 volunteers
Example Question #5 : How To Find The Solution For A System Of Equations
If x + 12 = 28, what is the value of (3x + 2) * (–x + 10)?
1300
–300
–1300
450
–180
–300
Solve for x, then plug into the formula to find the value. x = 28 – 12 = 16
(3 * 16 + 2) * (–16 +10) = –300
Example Question #2 : How To Find The Solution For A System Of Equations
Joey has $1.50. If he only has quarters and nickels and he has 14 coins total, how many nickels does he have?
10
6
5
8
3
10
Setting x and the number of quarters he has and y as the numbver of nickels. x + y = 14 (total coins), 0.25x + 0.05y = 1.50 (total amount). Substituting x = 14 – y from the first equation into the second, we get y = 10. Therefore Joey has 10 nickels.
Example Question #1 : Systems Of Equations
A soccer player kicks a ball at 8m/s. A player runs to receive it as soon as the ball as kicked at a speed of 4m/s. If the receiving player starts 12m ahead of the ball, how far does he travel before he gets the ball?
6 m
3 m
9m
15m
12m
12m
Setting t as the time elapsed we need to find when 8t = 12 + 4t (this is the distance traveled by the ball compared to the distance traveled by the player+difference from origin). Solving for t we get a travel time of 3 seconds. If the player runs for 3 seconds at 4m/s, the player travels 12m before receiving the ball.
Example Question #2001 : Sat Mathematics
Let f(x) = 2x2 – 3x + 1, and let g(x) = 13 – x. What is the distance between the points of intersection of f(x) and g(x)?
5√2
2√5
5√26
5
√26
5√2
First, we need to find the points of intersection between f(x) and g(x) by setting them equal to one another and solving.
f(x) = g(x)
2x2 - 3x + 1 = 13 – x
Add x to both sides.
2x2 – 2x + 1 = 13
Subtract 13 from both sides.
2x2 – 2x – 12 = 0.
Divide by two to make the coefficients easier to work with.
x2 – x – 6 = 0
Factor.
(x – 3)(x + 2) = 0
Set each of the factors equal to zero and then solve.
x – 3 = 0
x = 3
x + 2 = 0
x = –2
The two functions intersect where x = –2 and where x = 3.
The question asks us to find the distance between the points of intersection. Therefore, we will need to find the y-coordinates of the points of intersection when x = –2 and when x = 3.
When x = –2, f(–2) = g(–2) = 13 – (–2) = 15.
When x = 3, f(3) = g(3) = 13 – 3 = 10.
Thus, the points of intersection are (–2, 15) and (3, 10).
We can now use the distance formula given below.
The answer is 5√2
Example Question #12 : Systems Of Equations
What is the sum of x and y when you solve the following system of equations:
x – 3y = –5
2x + 5y = 12
5
2
3
4
1
3
We can solve this system of equations by using substitution. Rewriting the first equation, we get x = –5 + 3y. This equation gets substituted into the second equation, then solve for y. Once we know what y is, we can substitute the value into the first equation to find x. In this case, x = 1 and y = 2.
Example Question #221 : Equations / Inequalities
Sammy is counting his money when he notices he has two more quarters than dimes and the number of nickels are the same as the sum of quarters and dimes. The total cash he has on hand is $1.05. How many quarters does he have?
3
4
5
7
1
3
Define the variables as
x = # of dimes
x + 2 = # of quarters
x + x + 2 = # of nickels
In general, the formula for money problems in V1N1 + V2N2 + V3N3 = $total
0.10x + 0.25(x + 2) + 0.05(2x + 2) = 1.05
Solving the equation we see that there is one dime, three quarters and four nickels.
Example Question #222 : Equations / Inequalities
If x2 – y2 = 20, and x + y = 10, then what is the product of x and y?
24
–64
6
–4
–24
24
This problem involves a system of two equations. The first equation is x2 – y2 = 20, and the second equation is x + y = 10. Let us solve the second equation in terms of y, and then we can substitute this value into the first equation.
x + y = 10
Subtract y from both sides.
x = 10 – y
Substitute 10 - y for x in the first equation.
x2 – y2 = 20
(10 - y)2 – y2 = 20
We can use the FOIL method to find (10 – y)2.
(10 – y)2 = (10 – y)(10 – y) = 10(10) – 10y – 10y + y2 = 100 –20y + y2.
Now we can go back to our original equation and replace (10 – y)2 with 100 – 20y + y2.
(100 – 20y + y2) – y2 = 20
100 – 20y = 20
Subtract 100 from both sides.
–20y = –80
Divide both sides by –20.
y = 4.
Now that we know that y = 4, we can use either of our original two equations to solve for x. Using the equation x + y = 10 is probably simpler.
x + y = 10
x + 4 = 10
x = 6.
The original question asks for the product of x and y, which would be 4(6), which equals 24.
The answer is 24.
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