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Example 7-3b Objective Find the percent of a number

Example 7-3b Vocabulary None

Lesson 7 Contents Example 1Use a Proportion to Find a Percent Example 2Use Multiplication to Find a Percent Example 3Use Multiplication to Find a Percent

Example 7-1a SURVEYS Out of 1,423 adults surveyed, 30% said they knew the name of their mail carrier. How many of the people surveyed knew their mail carrier’s name? Write a ratio of those that knew the name to the total adults surveyed 1/3 number that knew name → total number in survey → Define the variable How many of the people surveyed knew their mail carrier’s name? Number that knew name = x Total number in survey is denominator

Example 7-1a SURVEYS Out of 1,423 adults surveyed, 30% said they knew the name of their mail carrier. How many of the people surveyed knew their mail carrier’s name? Remember: 30% refers to 30 out of 100 1/3 number that knew name → total number in survey → Write the percent in ratio form Put an = sign between the 2 ratios to make a proportion

Example 7-1a SURVEYS Out of 1,423 adults surveyed, 30% said they knew the name of their mail carrier. How many of the people surveyed knew their mail carrier’s name? Find the cross product 1/3 100  x 100  x = 1,423(30) Multiply 100x 100x = 42,690 Ask “What is being done to the variable?” The variable is being multiplied by 100 Do the inverse on both sides of the equal sign

Example 7-1a SURVEYS Out of 1,423 adults surveyed, 30% said they knew the name of their mail carrier. How many of the people surveyed knew their mail carrier’s name? Bring down 100x = 42,690 1/3 100  x 100  x = 1,423(30) 100x 100x = 42,690 Using the fraction bar, divide both sides by 100 Combine “like” terms x = x = Since cannot have part of a person, round to the nearest whole number x = 427 Add dimensional analysis x = 427 people knew carriers name Answer:

Example 7-1b SURVEYS Out of 765 students surveyed, 42% said that they watch some television after school before doing their homework. How many of the students surveyed watch some television after school before doing their homework? Answer: 321 students watch TV after school before doing homework 1/3

Example 7-2a What number is 120% of 24? Answer: x = 28.8 Change 120% to a decimal 1.2 Translate English to algebra =  24 The variable is by itself so multiply x = 28.8 x 2/3

Example 7-2b What number is 160% of 44? Answer: x = /3

Example 7-3a Find 25% of $600. Answer: x = $150 Change 25% to a decimal 0.25 Translate English to algebra x =  600 x = 150 3/3 The variable is by itself so multiply

Example 7-3b Find 80% of $450. Answer: x = $360 * 3/3

End of Lesson 7 Assignment Lesson 7:7Percent of a Number All