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PSSA Math Review

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  1. PSSA Math Review Lesson 33 Making Predictions

  2. Standards • E.4.1.2 Make predictions based on survey results or graphs (bar, line, circle, scatter plots, etc.)

  3. Example 1 • Last year, a store manager found that 3 of every 10 T-shirts she sold were black. If she expects to sell 500 T-shirts this year, how many can she predict will be black?

  4. Example 1 - Strategy • Use a proportion to predict the result. • Step 1: Set up a proportion. • Let t – the predicted number of black T-shirts. • 3/10 = t/500 • Step 2: Solve for t. • 3/10 = t/500 • 3 x 500 = 10 x t • 1,500/ 10 = t

  5. Example 1 - Answer • 150 = t • The store manager can predict that she will sell 150 black T-shirts.

  6. Example 3 Rodney surveys students at Lincoln Middle School to determine if they support going to school in the summer. This circle graph shows the results. Do You Support Going to School in Summer? 40% Yes 50% No 10% Not Sure

  7. Example 3 – Cont. There are 750 students at Lincoln Middle School. How many are likely to support going to school in the summer? 40% Yes 50 % No 10% Not Sure

  8. Example 2 - Strategy • Use the graph to make a prediction. • Step 1: Identify the percent that voted “Yes”. The graph shows that 40% of the students voted “yes”. • Step 2: Find 40% of the total number of students. There are 750 students. Find 40% of 750. 40% x 750 = 0.4 x 750 = 300

  9. Example 2 – Solution • Rodney can expect 300 students to support going to school in the summer.

  10. Example 3 For a science experiment, Deanna counts the number of fruit flies living in a container each day. This graph shows the results.

  11. Example 3 – Cont. • How many fruit flies can she expect on the 10th day?

  12. Example 3 - Strategy • Use the graph to make a prediction. • Step 1: Identify the pattern of the graph. The line is increasing from left to right. The rate of increase is slowing down as the line ”rolls over”. • Step 2: Extend the line. • Step 3: Use the extended line to predict the number for the tenth day. The number for the tenth day is about 40.

  13. Example 3 - Solution • Deanna should predict a population of 40 fruit flies on the tenth day.

  14. Sample Test Question

  15. Question 1 There are 425 people living in Willie’s apartment building. He asks 30 people about their preferences in the election for building president. Eighteen say they will vote for Mrs. Adams. If everyone votes, how many votes can Mrs. Adams expect in the election? • 255 • 295 • 345 • 395

  16. Question 1 - Solution • Set up a proportion: 18/30 = x/425 18 x 425 = 30x 7650/30 = x 255 = x Mrs. Adams can expect to receive 255 votes in the election.

  17. Question 2 This bar graph shows the number of cell phones owed by students in each grade at Booker T. Washington School. What is the best prediction for the number of cell phones owned by 9th graders?

  18. Question 2 – Cont. • What is the best prediction for the number of cell phones owned by 9th graders? • 240 • 250 • 270 • 300

  19. Question 2 - Solution • The best prediction is C. 270.

  20. Question 3 Which term best describes the correlation between cost and the number of radios sold? • Strong positive • Strong negative • Weak negative • No correlation

  21. Question 3 – Solution • Strong negative correlation.

  22. Question 4 How many radios are likely to be sold if the price is set at $34? • 24 • 28 • 32 • 38

  23. Question 4 - Solution • 32 radios will likely be sold. • C.

  24. Question 5 T.J. surveyed 60 students in his school about their after-school activities. The results are shown in this graph. 50% Sports 15% Band 25% Clubs 10% Yearbook

  25. Question 5 – Cont. If there are 800 students in the school, how many can T.J. expect to be in the band? • 9 • 60 • 80 • 120 50% Sports 15% Band 25% Clubs 10% Yearbook

  26. Question 5 - Solution First find 15% of 60. .15 x 60 = 9 9 students out of 60 are in the band. Next, set up a proportion. 9/60 = x/800 Cross multiply: 9 x 800 = 60x Solve for x: 7200/60 = x 120 = x

  27. Question 6 This graph shows the speed of a race car during its first few seconds off the starting line. If the pattern continues, how fast can you expect the car to go in the tenth second? • 170 miles per hour • 190 miles per hour • 210 miles per hour • 230 miles per hour

  28. Question 6 - Solution • B. 190 mph

  29. Open Ended Question Felicia buys a box of 200 filled chocolates. She eats 8 of them and finds that 3 are caramel-filled. • How many chocolates in the box can she expect to be caramel-filled? • Use what you know about making predictions to explain why your answer is correct. Use words and/or numbers in your explanation.

  30. Open Ended • A. She can expect 75 of the chocolates to be caramel-filled. • B. First you set up a proportion to help estimate the total amount that could possibly be caramel-filled. 3/8 = x/200 Next you cross multiply to solve for x. 3 x 200 = 8x Then you divide both sides by 8 to get x by itself. 600/8 = x Finally you solve for x and this will tell you an approximate prediction for the number of chocolates that will be caramel-filled. 75 = x