Population Problems
Video solutions to help Grade 7 students write and use algebraic expressions and equations to solve percent word problems related to
populations of people and compilations.
Related Topics:
Lesson
Plans and Worksheets for Grade 7
Lesson
Plans and Worksheets for all Grades
More
Lessons for Grade 7
Common Core For Grade 7
New York State Common Core Math Grade 7, Module 4, Lesson 16
Lesson 16 Student Outcomes
• Students write and use algebraic expressions and equations to solve percent word problems related to
populations of people and compilations.
Lesson 16 Classwork
Example 1
A school has 60% girls and 40% boys. If 20% of the girls wear glasses and 40% of the boys wear
glasses, what percent of all students wears glasses?
Exercises 1–2
1. How does the percent of students who wear glasses change if the percent of girls and boys remains the same (that
is, 60% girls and 40% boys) but of the 20% boys wear glasses and 40% of the girls wear glasses?
2. How would the percent of students who wear glasses change if the percent of girls is 40% of the school and the
percent of boys is 60% of the school, and 40% of the girls wear glasses and 20% of the boys wear glasses? Why?
Example 2
The weight of the first of three containers is 12% more than the second, and the third container is 20% lighter than the
second. The first container is heavier than the third container by what percent?
Exercise 3
3. Matthew’s pet dog is 7% heavier than Harrison’s pet dog, and Janice’s pet dog is 20% lighter than Harrison’s. By
what percent is Matthew’s dog heavier than Janice’s?
Example 3
In one year’s time, 20% of Ms. McElroy’s investments increased by 5%, 30% of her investments decreased by 5%, and 30%
of investments increased by 5%. By what percent did the total of her investments increase?
Exercise 4
4. A concert had 6,000 audience members in attendance on the first night and the same on the second night. On the
first night the concert exceeded expected attendance by 20% while the second night was below the expected
attendance by 20%. What was the difference in percent of concert attendees and expected attendees for both
nights combined?
Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.
You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.