Find the value of each expression mentally.

1. Find the value of . Explain or show your reasoning. You may use base-blocks if you find them helpful.

2. Here is how Priya finds the value of .

   1. Describe the steps in Priya’s method.

   2. How is Priya’s method similar to your method?
   3. Use Priya’s method to find the value of .

Tyler uses a different method to find the value of . Let’s compare Priya’s and Tyler’s work.

Priya's method

Tyler's method

1. How are these methods alike? How are they different? List as many similarities and differences as you can find.

2. Why do you think Tyler uses subtraction in his method?

3. Show how Tyler might record the process of finding the value of .