Foundations Sampler 2024

49 Lesson Plans 27 ©MathTeachersPress, Inc. Reproduction by anymeans is strictly prohibited. 27 Percent of a Number using Proportions Hector got 75% on his math test.There were 60 problems on the test. How many questions did he get correct? 75% as a ratio = 75 100 60 whole 0% 75% 100% n 60 75 100 number correct whole 100 n 75 60 100 n 4500 n 45 You can use a proportion to solve this problem. Should the60 bewritten above or below the fraction bar? Is 60 thewhole test or part of the test? Crossmultiply. Divide both sides by 100. Hector got____questions correct. n 60 75 100 1. = 3. = 2. = 4. = n __ 160 15 ___ 100 n __ 150 30 ___ 100 n __ 50 16 ___ 100 n __ 60 40 ___ 100 5. Shawn had 80% on his math test. There were 50 problems on the test. How many did Shawn get correct? _______ 7. 20% of the students bring their lunch to school. If there are 45 students in the school, how many bring their lunches? _______ 9. Drew made 45% of his free throw attempts. If he tried 200 free throws, how many did he make? _______ 6. Vernon got 84% correct on his math test.There were 25 questions on the test. How many questions did he get correct? _______ 8. Vicki got 60% on a social studies test.The test had 60 problems. How many problems did Vicki get correct? _______ 10. Leah got 65% problems correct on a science test.There were 40 questions on the test. How many problems did she get correct? _______ Solve for n . Write the proportion and solve. Let n represent the number correct out of60. Jason got 80% on a math test of 25 problems. Find the number of problems he got correct. Use a proportion and words to explain your answer. part 40 21 9 36 90 26 n=40 n=45 n=8 n=24 Objective: To use a proportion to find the percent or part of a whole. Materials: Fraction Bars, Percent Number Lines to 100 (Master 5) Finding a Part of a Whole Each pair of students or small group will need a set of fraction bars and a copy of Percent Number Lines to 100 (Master 5). Write on the board: There are 40 students in the art class. 25% of the students are boys. How many boys are in the class? Ask students to read the problem and use a picture to solve the problem. Pictures and solutions will vary. One possible solution: X X X X X X X X X X Explanation: If 25% are boys, 1 out of every 4 students are boys. I marked an X on 1 out of each group of 4. There were 25 X’s. You can also use fraction bars to visualize the whole-part relationships. What color bars would you use for 25%? (blue bars) Write on the board: What does this picture show us? (The shaded part shows the boys in the art class.) We can set up a proportion from this picture. We know that 25% means 25 parts out of 100, and that 100 is the whole. Write on the board: If we let x stand for the number of boys, where should we write x ? ( x goes above the bar because it is the part of a whole.) Where should we write 40? (40 goes below the bar because it represents the whole class.) How do we solve this proportion? (Use the cross products method.) 25 (parts) 100 (whole) 40 (whole class) x (part boys) = 25 (parts) 100 (whole) % boys 0% 0 n 40 25% 100% the whole art class Write on the board: There is another way to solve this proportion using equivalent fractions. First we reduce the fraction if possible. Next make both ratios have the same denominator. What number do you multiply by 4 to get 40? (10) We will multiply the fraction by 10 ⁄ 10 , which is the same as multiplying by one. Write on the board: Complete the example at the top of the page with the class. For questions 5 to 10, have students identify which numbers represent parts and which represent the whole. 25 100 40 x = 1 4 40 x 40 10 x = 10 1 4 = 40 x = = 10 10 25 100 40 x 25 40 = 100 x 1000 = 100 x 10 students = x = Percent of a Whole Sample of Scripting (Bold Type) You can also use fraction bars to visualize the whole-part relationships. What color bars would you use for 25%? (blue bars) Write on the board: % boys 0% 0 n 40 25% 100% the whole art class MH3 Lesson Plan Students use models to find percent.