Arithmetic Grade Four

Lesson One hundred and thirty-two: Problem Reconstruction

You know that you can check the answer to a division problem with a multiplication problem like this: 


	80 / 20 = 4   	  -->     20 x 4 = 80

        44 / 11 = 4       -->     11 x 4 = 44

        50 / 5 = 10       -->     5 x 10 = 50
  
        90 / 9 = 10       -->     9 x 10 = 90
Even when the division problem has a remainder we can still use multiplication. The only difference is that we will have to also add the remainder to the product like this:

Now take a look at these examples. 


       99 / 20 = 4 r19     -->    20 x 4 + 19 = 99

       89 / 30 = 2 r29     -->    30 x 2 + 29 = 89
  
       79 / 40 = 1 r39     -->    40 x 1 + 39 = 79

       99 / 50 = 1 r49     -->    50 x 1 + 49 = 99
Knowing this we can solve this kind of problem: 

      ___ /  5  = 2 r3

      CONVERT INTO A MULTIPLICATION PROBLEM:

      5 x 2 + 3 = ____

      ANSWER: 13
Try a few for yourself!

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