“Show All Totals”

There’s yet another method of adding with regrouping called “show all totals.” In this method, we first add the tens, show that entire total, then add the ones, show that entire total, and then add those two “totals” together to get the final total—the answer! We still want to keep our freeway lanes, though. Here’s how the example on page 122 would look:

Notice that with this “show all totals” method, instead of adding 9 + 3, we have to pay attention to the fact that we’re actually adding 90 + 30, and then we write the entire 120, being careful to keep everyone in their correct lanes before adding the ones column and then adding them all together.

Even though it’s a bit more work, some people prefer this way. Try the Game Time on page 123 with this method, and see which you like best!

In really big cities, they have big freeways—and that means more lanes! And with bigger numbers, everything works the same way as before….There are just more “lanes” to keep track of—more columns! Let’s do: 983 + 579. Whoa, this one looks kinda crazy! But we won’t crash if we keep all the cars in their correct lanes. And if it makes you happy, remember our pile of kitties. Let’s do it!

First, we write it out, with lanes marked:

Then we add up the ones: 3 + 9 = 12. Great! The 2 stays in the ones column, and the 1 gets to ride piggyback in the tens column. Next we add up the tens: 1 + 8 + 7 = 16. And “16 tens” means we have 6 tens and 1 hundred! So the 6 stays in the tens column and we put the 1 piggyback in the hundreds column. Next we add up the hundreds: 1 + 9 + 5 = 15. Whoa! What do we do now? Well…15 hundreds means we have 5 hundreds and 1 thousand! So we get to create a new thousands lane and put the 1 there.

We get 1 thousand, 5 hundreds, 6 tens, and 2 leftover ones—in other words, 1562. Done!

Answer: 983 + 579 = 1562