A bag contains 7 black socks, 12 white socks, and 17 red socks. If you pick one sock at random from the bag, what is the probability that it will NOT be white?
-
Solution
The bag contains a total of 7 + 12 + 17 = 36 socks.
Of these, 7 + 17 = 24 are NOT white.
Plug these two numbers (the number of colored socks and the total number of socks) into the formula for probability:
\(Probability = \frac{Target \;\, Outcomes}{Total \;\, Outcomes} = \frac{24}{36} = \frac{2}{3}\)
In the following figure, line a and line b are parallel and pass through the points shown. What is the equation for line b?
-
Solution
Line agoes “down 5, over 8,” so its slope is -5⁄8 Line b is parallel, so it has the same slope and has a y-intercept of –3.
Plug these numbers into the slope-intercept form to get the equation:
y = mx + b
y = -5⁄8x - 3
The ratio of adults to girls to boys on a class field trip was 1 : 4 : 5. If the trip included 6 more boys than girls, how many adults were with the group?
-
Solution
The ratio of girls to boys was 4 to 5, so write the ratio like this:
\(\frac{Girls}{Boys} = \frac{4}{5}\)
If you let g equal the number of girls on the trip, you know that the number of boys was g + 6.
Plug these values into the ratio:
\(\frac{g}{g + 6} = \frac{4}{5}\)
Cross-multiply and solve for g:
5g = 4(g + 6)
5g = 4g + 24
g = 24
So now you know that 24 girls went on the field trip, and you’re ready to find the number of adults.
The ratio of adults to girls was 1 : 4.
That is, the number of adults was 1⁄4 the number of girls, so you know that 6 adults attended the field trip.
Two variables, v and w,are inversely proportional such that when v = 7, w = 14. What is the value of w when v = 2?
-
Solution
The variables v and w are inversely proportional, so for some constant k,the equation vw = k is always true.
Thus, when v = 7 and w = 14:
vw = (7)(14) = 98
So k = 98.
When v = 2, you can find w like this:
vw = 98
2w = 98
w = 49
In the following figure, what is the value of x in terms of y?
-
Solution
The two legs of the triangle are of lengths y and 3y, and the hypotenuse is of length y.
Plug these values into the Pythagorean theorem:
a2 + b2 = c2
y2 + (3y)2 = x2
Simplify and solve for x in terms of y:
y2 + 9y2 = x2
10y2 = x2
\(\sqrt{10y^{2}} = x \Rightarrow y\sqrt{10} = x\)
If f(x) = x2 + 9 and g(x) = 24 + 4x,what is the value of \(\frac{f\left ( 4 \right )}{g\left ( -1 \right )}\)?
-
Solution
To start, find the values of f(4) and g(–1):
f(4) = 42 + 9 = 16 + 9 = 25
g(–1) = 24 + 4(–1) = 24 – 4 = 20
Thus:
\(\frac{f\left ( 4 \right )}{g\left ( -1 \right )} = \frac{25}{20} = 1.25\)
In the following figure, what is the midpoint of \(\overline{UV}\)?
-
Solution
Plug the values (–3, –7) and (1, 8) into the midpoint formula:
\(Midpoint = \left ( \frac{x_{1} + x_{2}}{2}, \frac{y_{1} + y_{2}}{2} \right )\) = \(\left ( \frac{-3 + 1}{2} , \frac{-7 + 8}{2} \right ) = \left ( -1 , \frac{1}{2} \right )\)
Two values of m satisfy the equation |5m – 11| – 3m = 9. What is the result when you multiply these two values together?
-
Solution
To begin, isolate the absolute value on one side of the equation:
|5m – 11| – 3m = 9
|5m – 11| = 9 + 3m
Next, split the equation into two separate equations and remove the absolute value bars:
5m – 11 = 9 + 3m ; 5m – 11 = –(9 + 3m)
Solve both equations for m:
5m = 20 + 3m ; 5m – 11 = –9 – 3m
2m = 20 ; 5m = 2 – 3m
m = 10 ; 8m = 2
m = 0.25
The product of these two values is 10 × 0.25 = 2.5.
What is the formula of a line that is perpendicular to y = 1⁄3x + 9 and includes the point (3, 4)?
-
Solution
Any line perpendicular to y = 1⁄3x + 9 has a slope of –3.
So you can rule out Choices (A), (B), and (C).
Plug this number into the slope-intercept form, along with the x- and y-coordinates for the point (3, 4):
y = mx + b
4 = –3(3) + b
4 = –9 + b
13 = b
Now plug the slope m = –3 and the y-intercept of 13 into the slope-intercept form to get the formula of the line:
y = –3x + 13
If 15% of n is 300, what is 22% of n?
-
Solution
Write “15% of n is 300” as an equation:
0.15n = 300
Now solve for n:
\(n = \frac{300}{0.15} = 2000\)
Twenty-two percent of 2,000 is 440.