standard_description: Understand that positive and negative numbers are used together to describe quantities having opposite directions or values (e.g., temperature above/below zero, elevation above/below sea level, credits/debits, positive/negative electric charge); use positive and negative numbers to represent quantities in real-world contexts, explaining the meaning of 0 in each situation.
problem_activity: You are shoveling snow from the sidewalks around your neighborhood after a big snowstorm. You work at a steady rate, shoveling 10 feet of sidewalk in 40 minutes.
a.   At this rate, how long will it take you to shovel 75 feet of sidewalk?
b.   At this rate, how many feet of sidewalk will you have shoveled after 2 hours?


aligns: no