Pre-Algebra : Graphing

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #1 : Graphing

What is the slope of the line:

 \(\displaystyle \small \small y=90x+1\)

Possible Answers:

\(\displaystyle \small -90\)

\(\displaystyle \small 1\)

\(\displaystyle \small -1\)

\(\displaystyle \small 90\)

\(\displaystyle \small x\)

Correct answer:

\(\displaystyle \small 90\)

Explanation:

Using the equation: \(\displaystyle y=mx+b\) you know that the slope is m.

When you look at the equation:

\(\displaystyle \small y=90x+1\) you see that the value of \(\displaystyle \small m\) is \(\displaystyle \small 90\)

Example Question #1 : Analyzing Graphs And Figures

Histogram

Refer to the above graph. Clark, a sixth grader at Polk, outscored 100 of the students who took the test. What could his score have been?

Possible Answers:

\(\displaystyle 735\)

\(\displaystyle 335\)

\(\displaystyle 535\)

\(\displaystyle 635\)

\(\displaystyle 435\)

Correct answer:

\(\displaystyle 635\)

Explanation:

\(\displaystyle 6 + 18 + 30 + 40= 94\) students achieved scores between 200 and 600, and Clark outscored all of them.

\(\displaystyle 6 + 18 + 30 + 40 + 16= 110\) students achieved scores between 200 and 700; Clark did not outscore all of them. 

Therefore, his score fell in the range from 601 to 700, making 635 the only plausible choice of the five.

Example Question #2 : Analyzing Graphs And Figures

Histogram

Refer to the above bar graph.

How many students at Polk Middle School scored from 301 to 700 on the math portion of the SCAT?

Possible Answers:

The answer to the question cannot be derived from the graph.

\(\displaystyle 104\)

\(\displaystyle 88\)

\(\displaystyle 110\)

\(\displaystyle 114\)

Correct answer:

\(\displaystyle 104\)

Explanation:

   \(\displaystyle 18\) students scored in the 301-400 range.

   \(\displaystyle 30\) students scored in the 401-500 range.

   \(\displaystyle 40\) students scored in the 501-600 range.

\(\displaystyle \underline{+16}\) students scored in the 601-700 range. Add these:

\(\displaystyle 104\) students in all scored anywhere from 301-700.

Example Question #1 : Graphing

Find the slope of the line between the points \(\displaystyle (2,4)\) and \(\displaystyle (4,7)\).

Possible Answers:

\(\displaystyle \small \frac{2}{3}\)

\(\displaystyle \small -\frac{2}{3}\)

\(\displaystyle \small \frac{3}{2}\)

\(\displaystyle \small -\frac{3}{2}\)

Correct answer:

\(\displaystyle \small \frac{3}{2}\)

Explanation:

Recall the slope formula:

\(\displaystyle \small \small m=\frac{rise}{run}=\frac{y2-y1}{x2-x1}\)

Plug in the two given points:

\(\displaystyle \small m = \frac{y2-y1}{x2-x1}= \frac{7-4}{4-2}\)

\(\displaystyle \small m = \frac{7-4}{4-2} = \frac{3}{2}\)

The slope of the line is \(\displaystyle \small \frac{3}{2}\).

 

Example Question #4 : Graphing

Histogram

Refer to the above bar graph.

What percent of the students achieved a score above 400?

Possible Answers:

\(\displaystyle 50 \%\)

\(\displaystyle 55 \%\)

\(\displaystyle 75 \%\)

\(\displaystyle 80 \%\)

\(\displaystyle 66 \frac{2}{3} \%\)

Correct answer:

\(\displaystyle 80 \%\)

Explanation:

30 students achieved a score of 401-500; 40 students achieved a score of 501-600; 16 achieved a score of 601-700; 10 achieved a score of 701-800. Add these:

\(\displaystyle 30 + 40 + 16 + 10 = 96\)

The number of students who took the test is the sum of the students who finished in the six ranges:

\(\displaystyle 6 + 18 + 30 + 40 + 16 + 10 = 120\)

The question is now to find out what percent 96 is of 120, which can be calculated as follows:

\(\displaystyle \frac{96}{120} \times 100 \% = 80 \%\)

Example Question #5 : Graphing

What is the slope of the line that contains the points  

\(\displaystyle (2,4)\) \(\displaystyle and\) \(\displaystyle (3,4)\) ?

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle \textup{Undefined}\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle 1\)

\(\displaystyle 0\)

Correct answer:

\(\displaystyle 0\)

Explanation:

Using the equation:

 \(\displaystyle \frac{y_{1}-y_{2}}{x_{1}-x_{2}}\) 

you plug in your points (2,4) and (3,4)

\(\displaystyle \frac{4-4}{3-2}\)  \(\displaystyle or\)   \(\displaystyle \frac{0}{1}\) 

Example Question #5 : Analyzing Graphs And Figures

Below is the list of candidates for Student Council president, along with the number of votes each won:

\(\displaystyle \begin{matrix} \textrm{\underline{Student}} &\textrm{\underline{Votes}} \\ \textrm{Phillips}\; & 105\\ \textrm{Young}\; \; \;& 83\\ \textrm{Harris}\; \; \; &64 \\ \textrm{McCain}\;& 45\\ \textrm{Zimmer}\; \; & 39 \end{matrix}\)

What percent of the students voted for neither Phillips nor Young (nearest tenth)?

Possible Answers:

\(\displaystyle 36.8 \%\)

\(\displaystyle 21.3 \%\)

\(\displaystyle 56.0 \%\)

\(\displaystyle 78.7 \%\)

\(\displaystyle 44.0 \%\)

Correct answer:

\(\displaystyle 44.0 \%\)

Explanation:

\(\displaystyle 105+83+64+45+39 = 336\) students voted; of those students, \(\displaystyle 64+45+39 = 148\) voted for a candidate other than Phillip or Young. To convert this to a percent, use this proportion and solve for \(\displaystyle p\) :

\(\displaystyle \frac{p }{100}= \frac{148}{336}\)

\(\displaystyle \frac{p }{100} \cdot 100 = \frac{148}{336} \cdot 100\)

\(\displaystyle p = \frac{14,800}{336} \approx 44.0 \%\)

 

Example Question #2 : Analyzing Graphs And Figures

Pie_graph

 

Four candidates ran for mayor of Jackson City; the above circle graph shows the share of the vote that each won.

According to a city ordinance, a candidate must win more than 50% of the vote to win the election; if this does not happen, the two candidates who win the most votes will face each other in a runoff election. Based on the above graph, which of the following is the outcome of the vote?

Possible Answers:

Mills and King will face each other in a runoff.

Jones won the election outright.

Mills won the election outright.

Jones and King will face each other in a runoff.

Mills and Jones will face each other in a runoff.

Correct answer:

Mills and Jones will face each other in a runoff.

Explanation:

By comparing the sizes of the sectors, it can be seen that Mills won the largest share of the vote - but not at least one half of it - and Jones won the second-largest share. Therefore, they will face each other in a runoff.

Example Question #193 : Data Analysis And Probability

Four candidates ran for mayor of Johnston City. The results are below.

\(\displaystyle \begin{matrix} \textrm{\underline{Candidate}} & \textrm{\underline{Votes}} \\ \textrm{Allen } & 4,128 \\ \textrm{Carter } & 2,177 \\ \textrm{Johnson } & 5,813 \\ \textrm{Wayne } & 1,578 \end{matrix}\)

Which of the following is the best estimate of the percent of the vote won by Johnson?

Possible Answers:

\(\displaystyle 10\) %

\(\displaystyle 50\) %

\(\displaystyle 20\) %

\(\displaystyle 30\) %

\(\displaystyle 40\) %

Correct answer:

\(\displaystyle 40\) %

Explanation:

Since we are asking for an estimate, one way to work this problem is to round each candidate's vote tally to the nearest thousand, then adding the rounded numbers:

\(\displaystyle 4,178 + 2,177 + 5,813 + 1,578\)

\(\displaystyle \approx 4,000 + 2,000 + 6,000 + 2,000 = 14,000\)

Johnson's share of the vote is about 6,000 of those approximately 14,000 votes, or \(\displaystyle \frac{6,000}{14,000} = \frac{6}{14} = \frac{3}{7}\)

As a percent, \(\displaystyle \frac{3}{7}\) is equal to:

\(\displaystyle \frac{3}{7} \cdot 100 = \frac{300}{7}\)

\(\displaystyle 300 \div 7 \approx 43\)

Therefore, 40% is the best estimate of the choices we are given.

Example Question #2 : Tables

Pie_graph

Five candidates ran for mayor of Madison City; the above circle graph shows the share of the vote that each won. Which of the following would be the most reasonable estimate of the percent of the vote Lyle won?

Possible Answers:

\(\displaystyle 5\) %

\(\displaystyle 40\) %

\(\displaystyle 10\) %

\(\displaystyle 30\) %

\(\displaystyle 20\) %

Correct answer:

\(\displaystyle 10\) %

Explanation:

The sector representing Lyle is roughly one-tenth to one-eighth of the circle - in other words, 10-12 % of it. This is the approximate percent of the vote won by Lyle.

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