Title
Grade
SBAC
Assessment
Claim
Speedy Texting
7
1: Concepts and Procedures ―Students can explain and apply mathematical concepts and interpret and carry out mathematical procedures with precision and fluency.
3: Communicating Reasoning
―Students can clearly and precisely construct viable arguments to support their own reasoning and to critique the reasoning of others.
Learning Goal Students will be able to write algebraic expressions and equations given real-life situations and will be able to interpret their solution.
Item Type
Standards
Performance Task
7EE.3: Solve multi-step real-life problems posed with positive and negative rational numbers in any form.
7EE.4: Use variables to represent quantities in a realworld or mathematical problem, and construct simple equations to solve problems by reasoning about the quantities.
7EE.4.a: Solve word problems leading to equations of the form px + q = r , where p , q , and r are specific rational numbers. Solve equations of these forms fluently.
Identify the sequence of the operations used in each approach.
Practice(s)
Depth of
1, 4, 6
2, 3
Knowledge
Task Overview Students will write algebraic expressions, write and solve equations, and explain their sequence of operations used to solve each equation. Students will interpret the meaning of a variable in the context of a given real-life scenario and will write a real-life scenario given an equation.
Teacher
Resource
A U.S. teenager has scooped fifty thousand dollars in prize money at the national phone speed texting competition. http://www.youtube.com/watch?v=GvVbJwAWtes

Speedy Texting
James wants to compete in the international speed-texting competition next year where participants compete on text speed and accuracy. James’ current text speed is 2 characters per second. James has found that his texting speed increases at a rate of ½ a character per second for each month that he practices.
1a. What is James’ new texting speed if he practices for just 1 month? __________
1b. What is James’ new texting speed if he practices for 2 months? ____________
1c. What is his new texting speed if he practices for 3 months? _____________
1d. Write an algebraic expression that gives James’ texting speed for m months of practice
2a. Last year’s winner at the international speed-texting competition won by texting
8 characters per second. Write an equation to model the number of months it will take James to reach this texting speed.
2b. Use the equation created in 2a to determine how many months of practice it will take before James’ texting speed reaches last year’s record.
2c. Explain the steps taken to solve your equation from 2b.
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3a. Lydia would also like to compete in the same speed-texting competition as
James. She currently texts at a rate of 4 characters per second, but will only have
10 months to practice before the competition. If Lydia wants to text at least 8 characters per second, like James, then the equation 10x + 4 = 8 could be used to model this situation. Find x.
3b. Explain what the variable x represents in this equation.
3c. How is this variable the same or different from the variable in the equation from question 2a?
4. Consider the equation 8x + 5 = 37. Write a real-life scenario that this equation could model.

Credit for specific aspects of performance should be given as follows:
1a. 2 ½ characters per second (correct answer)
1b. 3 characters per second (correct answer)
1c. 3 ½ characters per second (correct answer)
1d. Expression 2 + ½m or ½m + 2
2a. Equation 2 + ½m = 8 or ½m + 2 = 8
2b. Solve the equation ½m + 2 = 8 using inverse operations (subtract 2 from both sides of the equation, and multiply by 3 or divide by ½ on both sides).
2c. Explanation should include

Subtract 2 or put the additive inverse of 2 on both sides of the equation

Divide by ½ or put the multiplicative inverse of ½ on both sides of the equation
3a. Correct steps to solve the equation 10x + 4 = 8

Subtract 4 or put additive inverse of 4 on both sides

Divide by 10 or put multiplicative inverse of 10 on both sides

Correct answer of x = 4/10, 2/5, or 0.4
3b. Response should include:

X represents Lydia’s texting speed increase or change each month of practice
3c. Response should include:

The equation in part 2a represents the months of practice to get given speed

The equation in part 3 represents the rate of increase in texting speed for each month of practice
4. Response should include:

A real-life scenario that can appropriately models the given equation. o For example: Molly needs to save $37 to buy a new dress for the next school dance. Molly already has $5 saved. If
Molly can solve $8 an hour babysitting, how long will it take Molly to save enough to buy the dress?
Points
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
1 point
Total Points
Total Points
4 points
4 points
3 points
1 point
1 point
1 point