Practice Selecting Student Explanations
To practice selecting explanations, follow the steps to view a variety of student explanations for the same question.
 Choose a student video to watch.
 Decide which explanation you would select.
 View the explanation selected by the MRI author team.

Question: 99 + 17
Question: Molly ran 1.5 miles for 20 days
Question: Compare 3⁄8 and 5⁄6
Loading the video player …
Which explanation would you select?
 Counted on by 1s
 Used standard algorithm to add
 Added 90 + 10, 9 + 7, and then 100 + 16
 Added 99 + 10 and then 109 + 7
 Added 100 + 17 and then subtracted 1
 Changed problem to 100 + 16
 Gave other reasonable explanation
 Guessed, did not explain, or gave faulty explanation
 Used standard algorithm to multiply
 Multiplied 20 x 1 and then 20 x 0.5
 Multiplied 1.5 x 2 and then 3 x 10
 Multiplied 1.5 x 10 and then 15 x 2
 Multiplied 15 x 2 and then adjusted the decimal point
 Gave other reasonable explanation
 Guessed, did not explain, or gave faulty explanation
 Converted to common denominators
 Compared to 1/2 or 50%, or 1 or 100% (e.g., 5/6 is more than 1/2 and 3/8 is less than 1/2)
 Explained that eighths are smaller than sixths and there are fewer eighths
 Converted to decimals or percents
 Gave other reasonable explanation
 Guessed, did not explain, or gave faulty explanation
View the explanation selected by the MRI author team.
Added 100 + 17 and then subtracted 1.
Alberto's reasoning most clearly matches this explanation. 
