Recently we discussed some great examples of using counters for splitting numbers apart to see that 4+0=4 and 3+1=4.
Now let's turn our attention to groups of 10 for adding and subtracting. The goal is to introduce concretely how we group and ungroup tens for adding and subtracting in base-10. Notice that I did not say carry and borrow.
Use fewer than 20 counters and start to break up numbers the same way.
What I just wrote sounds a bit clinical. How have you or can you do this process organically or by "living math out loud"?
Here are some on-line virtual counters for the discussion above. Try it out yourself first and see what comes to you.
Now let's turn our attention to groups of 10 for adding and subtracting. The goal is to introduce concretely how we group and ungroup tens for adding and subtracting in base-10. Notice that I did not say carry and borrow.
Use fewer than 20 counters and start to break up numbers the same way.
- Create numbers greater than 10 using counters of your choice. Be sure to group 10 and push them to the left leaving the remainders to the right. (15 would be a group of 10 and 5 single pieces.)
- Take the next step and put two groups of counters together that are each less than 10. For example a group of 8 and a group of 7 counters are added separately and then mushed together. Make the group of 10 with the 5 remainder.
- With subtraction, let's subtract 7 from 12. To subtract take away counters. The counters are arranged in a pile of a 10 and 2 singles. To subtract the 7, first ungroup the 10 pile and bring it back to the singles pile. Then subtract the counters to find the five remaining.
What I just wrote sounds a bit clinical. How have you or can you do this process organically or by "living math out loud"?
Here are some on-line virtual counters for the discussion above. Try it out yourself first and see what comes to you.
-Organizing in Base-10: http://nlvm.usu.edu/en/nav/frames_asid_152_g_1_t_1.html?from=category_g_1_t_1.html
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