Friday, October 15, 2010

8-2 Divide multiples of 10, 100, and 1,000

This idea really only needs you to know your basic multiplication facts, the rest if just adding zeros.

#1) 300 divided by 6.
I want you to draw a line cutting the number 300 into two pieces; 30 and 0. Now that we've narrowed things down, let's count by 6's until we get to thirty. 6, 12, 18, 24, 30. That took us 5 times. Write a 5 above the thirty, and the number 30 underneath. Don't forget to subtract the 30 and 30. That's easy, you get 0. Now that poor other zero is there all by himself. You can't count by 6's until you get to 0, that's silly. Think of it this way, 3 times what gives you 0? 0! So write that 0 on top as well. And you get an answer of 50.

#16) The input output table
The directions for this one tells us to divide by 5. The first input number is 1,500. According to the directions, we need to divide 1,500 by 5. Draw this with the 1,500 under the house and the 5 outside the front door. I sure hope you understand what that means. Now draw a line cutting 1,500 into two pieces; 15 and 00. Super easy now. Count by 5's until you get to 15. 3! Add in your filler zeros above the other two, giving you the answer 300!

#17)61 divided by 3.
Re-write this problem with the 61 inside the house and the 3 outside. Now cut the 61 in half with a line. Super easy now! Count by 3's until you get to 6. 3, 6. That took us 2 times. So write a 2 above the 6, and the 6 below the 6. Now subtract the 6 and 6. We get Zero. BUT! That poor 1 is all by himself. Bring him down, now let's count by 6's until we get to 1. Uh-oh, can't do it. Now listen very carefully. You HAVE to put a 0 above the 1, because we can't leave that place value empty. So far we now have 20 as our answer, but that pesky left over 1 needs to be a remainder. So your final answer is 20 r1

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