2-Digit Mental Mathematics

Strand: Number
Outcomes: 6 and 7

Step 2: Determine Evidence of Student Learning

Guiding Questions

What evidence will I look for to know that learning has occurred?
What should students demonstrate to show their understanding of the mathematical concepts, skills and Big Ideas?

Using Achievement Indicators

The following indicators may be used to determine whether or not students have met these specific outcomes. Can students:

add two given 2-digit numerals, using a mental mathematics strategy, and explain or illustrate the strategy?
explain how to use the "adding from left to right" strategy; e.g., to determine the sum of
23 + 46, think 20 + 40 and 3 + 6?
explain how to use the "taking one addend to the nearest multiple of 10 and then compensating" strategy; e.g., to determine the sum of 28 + 47, think 30 + 47 – 2 or
50 + 28 – 3?
explain how to use the "using doubles" strategy; e.g., to determine the sum of 24 + 26, think 25 + 25; to determine the sum of 25 + 26, think 25 + 25 + 1 or doubles plus 1?
apply a mental mathematics strategy for adding two given 2-digit numerals?
subtract two given 2-digit numerals, using a mental mathematics strategy, and explain or model the strategy used?
explain how to use the "taking the subtrahend to the nearest multiple of 10 and then compensating" strategy; e.g., to determine the difference of 48 – 19, think 48 – 20 + 1?
explain how to use the "adding on" strategy; e.g., to determine the difference of 62 – 45, think 45 + 5, then 50 + 12 and then 5 + 12?
explain how to use the "using doubles" strategy; e.g., to determine the difference of 24 – 12, think 12 + 12 = 24?
apply a mental mathematics strategy for subtracting two given 2-digit numerals.

Sample behaviours to look for related to these indicators are suggested for some of the activities listed in Step 3, Section C, Choosing Learning Activities.