## Friday, April 8, 2016

### Math problem of the week: Common Core Math Goal 5.OA1-inspired problem

A sample 5th grade problem from the Common Core resources of the New York-based Lake Shore Central School District:

Operations and Algebraic Thinking:

5.OA1: Write and Interpret numerical expression.

Maxwell bought a new pair of skis for \$350. He put \$110 down and received a student discount of \$30. His mother gave him 1/2 of the balance for his birthday. Which of these expressions could be used to find the amount Maxwell still owes on the skis?

A. 350−110+30÷2
B. 350−(110−30)÷2
C. [350−(110−30)÷2]
D. [350−(110+30)]÷2

Extra Credit:

Besides “write and interpret numerical expression,” what other skills does this problem involve? Consider the ESL student, the language-impaired student, or the student on the autistic spectrum, and:

1. Idiosyncratic meanings that override literal meaning: “put money down;” “balance.”

2. Knowledge of transactional “schema”: the special discount; the down payment.

A rewrite that more specifically measures 5.OA1:

A pair of skis costs \$350. Students get a price reduction of \$30. A student has \$110. His mother gives him 1/2 of what he still needs to buy the skis. Which of these expressions shows the amount he now needs?

A. 350−110+30÷2
B. 350−(110−30)÷2
C. [350−(110−30)÷2]
D. [350−(110+30)]÷2