Treat it like money!

We have already learned a few tips on how to quickly add numbers.  Here is another great tip to use, especially when adding 3-digit or 4-digit numbers!

Here is our first example.
What is the sum of 413 + 769?  If we treat it like money, we are breaking it into two separate usable parts.  Rewrite it and solve it as the sum of $4.13 + $7.69.
Step 1--Add the numbers to the left of the decimal, or what we think of as the number of dollars.  We know that 7 + 4 = 11.
Step 2--Add the numbers to the right of the decimal, or more simply, the value of the cents or coins.  13 + 69 = 82.
Step 3--Combine the answers from Step 1 and Step 2.  The solution is $11.82, but since the question was not asking for dollars and cents, we must remove the decimal.  413 + 769 = 1182.
Done!

Let's try another one.
Bob is donating bottled waters for 2 upcoming charity events.  Each person will receive one bottle of water at the entrance.  Last year the attendance at each event was 1142 and 1217.  If the attendance this year is expected to be the same as last year, how many bottles should Bob purchase?

Solution:
Rewrite the problem as $11.42 + $12.17.
Step 1--Add 11 + 12, which is 23.
Step 2--Add  42 + 17, which is 59.
Step 3--Combine the answers for our solution.  $11.42 + $12.17 = $23.59, but we must remove the decimal and $.  1142 + 1217 = 2359!

Cases of bottled waters commonly have 24 bottles.  If Bob wants to round the amount to 2400, he quickly knows that he should buy 100 cases.

Practice a few more of your own examples, and remember to teach this practical tip to a friend!