Solve problems involving time intervals by adding and subtracting on the number line

In this lesson, students continue problem solving with time. They measure minute intervals and then add and subtract the intervals to solve problems. (For example, "I practiced the piano for 25 minutes and the clarinet for 30 minutes. How long did I spend practicing my instruments?") Calculations with time in this lesson are appropriate for Grade 3: they do not cross over an hour or involve students converting between hours and minutes.