In this activity, students perform multi-digit addition and subtraction to solve problems in context and assess the reasonableness of answers. The situation can be approached in many different ways, such as:

• Arrange the numbers in some way before adding or subtracting.
• Add the largest numbers first.
• Add two numbers at a time.
• Add numbers with the same number of digits.
• Subtract each expense, one by one, from the amount collected.

Students reason abstractly and quantitatively when they make sense of the situation and decide what operations to perform with the given numbers (MP2).

This activity uses MLR6 Three Reads. Advances: reading, listening, representing

• Invite students who solved the problem in different ways to share.

In this activity, students practice adding and subtracting multi-digit numbers through a game. Students draw several cards containing single-digit numbers, arrange the cards to form two numbers that would give the greatest and the least sums and differences. To meet these criteria, students look for and make use of structure in base-ten numbers (MP7).

• “When making the greatest sum possible, how did you decide which digits to choose for each place?”
• “How can thinking about place value help you form numbers to make the greatest possible sum (or least possible sum)?”

• Ask students to share their sums and differences and the rest of the class to check if they actually are the greatest and least sums and differences.
• “After playing a couple of rounds, did you figure out how to find the greatest or least sum or difference more quickly? How?” (Answers vary. Students say they estimated using the place value of the first digits of each number.)