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if i have 436 x 67 how do I get the product by subtracting?

My daughter has this problem:

 

Laura found 67 x 436 by multiplying and subtracting. Show how Laura found the product. I showed my daughter the multiplication method and then used division for the subtraction. Was this right?

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thank all of you soooo much! this should make things easier for me when we have to study for a math test!! i was just completely stumped by this fourth grade problem! need to boost my math skills I guess. I still have 8 more years of problems getting difficult for her, not to mention 2 younger brothers that will be going through the same thing, lol! THANKS AGAIN!!!!

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3 Answers

Hi Barb, 

The typical way to evaluate 67 x 436 is by multiplying and adding: (60 + 7) x 436.  Usually this is written as:

      436

x      67

---------

     3052 = 436 x 7

+ 26160 = 436 x 60

----------

    29212

Alternatively, you could evaluate 67 x 436 by multiplying and subtracting: (70 - 3) x 436.

      436

x      67

---------

   30520 = 436 x 7

-   1308 = 436 x 3

---------

   29212

Although you get to the same answer both ways, one or the other method may be easier.  For example, consider 48 x 713 = (40 + 8) x 713 = (50 - 2) x 713.  In this case, multiplying and subtracting is easier (for me!) because it involves multiples of 5's and 2's rather than of 4's and 8's.

Hi, Barb.

I do not know the particular method this assignment is looking for, but here is one way to get the product using mutiplication and subtraction:

Round 67 to 70.

Multiply 436 x 70, which is an easier multiplication problem.

Since 70 is 3 more than 67, this product has 3 extra "436"s. From the product, subtract 436 three times.

436 x 70 = 30,520

30,520 -436 = 30,084

30,084 -436 = 29,648

29,648 -436 = 29,212

 

67 x 436

= 436 x (70-3) <== since 67 = 70 - 3

= 436 x 70 - 436 x 3 <==Multiplication and subtraction

= 30520 - 1308

= 29212