A little help please .. 29 x 28 = ?

Question

I can't remember how to do these types of multiplication. I need to know HOW to get the answer (not the answer itself)

29 x 28 = ?

Answer 1

812

it's easier if you put the 29 above the 28

   29

x 28                                

--------  

232

580

____

812          

Answer 2

Write it out like this

  29

x28

Multiply the bottom right number (8) by 9  = 72

Leave the 2 below the 8 and 9

Carry the 7 to the tens column (second from right)

Multiply 8 by 2 = 16 and add 7 to that which makes 23

So 28 times 8 is 232

Now add a zero initially before doing anything below 232

2 times 9 is 18...draw the 8 beside the 0 to get 80

Carry the 1 and multiply 2 x 2 to get 4 (plus 1 ) = 5

So 29 times 20 is 580

Now add 580 to 232 and you get your answer: 812

  29

x28

=====

  232

+580

---------

812

Hope it helps!

Answer 3

Remember to stack them.

  29

x28

Mulitply 8 x 29. (8x9) + (8x20)  write that down

   232

       0 (drop a zero in the first spot) then multiply 2 x 29 and write that down.

you get:

   232

   580

now add these two numbers.

812

Answer 4

Here's one way.  I find this method very fast for dealing with numbers like these.  You can do this in your head.

Select a numerical value for x which is close to the two numbers to be multiplied, and which can be easily squared in your head.  So, in this case, let x = 30.  Then 29 = x - 1, and 28 = x - 2.

Now you can use the general product of (x - 1) and (x - 2) to find the product of 29 x 28.

Multiplying (x - 1) and (x - 2) in our head, we get x² - 3x + 2.  Then, plugging x = 30 into the expression and calculating the sum in our head, we get this:  (30)² - 3 (30) + 2 = 900 - 90 + 2 = 810 + 2 = 812.  Therefore, 29 x 28 = 812.

Answer 5

if you mean mentally, easiest should be

29 x 28 = (30 - 1) x 28 = 28 x 30 - 28 = 840 - 28 = 812