I decided to upload the method we used in class for adding pairs to 100 and 1000.
I have this sum:
730 + _ = 1000.
Step 1:
Find how many more to arrive to 100. So, how many numbers do you need so that from 73 you arrive to 100?
73 + _ = 100
Step 2:
Look at the
unit digit number. It is 3. How many more to 10? The answer is
7. So, if I need 7 to make 10, than I need 7 to make the
next ten of 73 which is 80. So:
73 +
7 = 80.
Step 3:
Now, I need to arrive to 100. How many more to arrive to 100?
20 more. So,
80 +
20 = 100.
Step 4:
How many numbers did I add altogether?
7 + 20 = 27.
Step 4:
Now we know that you need 27 more with 73 to make 100. So,
73 +
27 = 100.
If you arrived there, now you can write the matching pair to make 1000. In class I told you that
each number in a pair totalling 1000 is ten times the matching pair totalling 100. So therefore, if
73 + 27 = 100, than
730 + 270 = 1000.