# Help with multiplying large numbers by hand

• Feb 11th 2009, 01:15 PM
Stillen GLE
Help with multiplying large numbers by hand
Aight Guy's I don't really understand it, I could never do the math problems in order, I recently came from double figures on top and bottom, Now I doing triple digits on top and bottom, I am currently going to tutoring for math and other thing's my teacher is having me play a game called Latice however you say it.

any tips would be great, I really wanna get into a 4 year school, I currently graduated high school last year, I just didn't get everything I needed to go to a 4 year school etc. so I am going to Huntington Learning Center for extra help they're helping alot I just wanna little extra for when I am not there.
• Feb 11th 2009, 01:29 PM
TheMasterMind
Quote:

Originally Posted by Stillen GLE
Aight Guy's I don't really understand it, I could never do the math problems in order, I recently came from double figures on top and bottom, Now I doing triple digits on top and bottom, I am currently going to tutoring for math and other thing's my teacher is having me play a game called Latice however you say it.

any tips would be great, I really wanna get into a 4 year school, I currently graduated high school last year, I just didn't get everything I needed to go to a 4 year school etc. so I am going to Huntington Learning Center for extra help they're helping alot I just wanna little extra for when I am not there.

Post a specific problem(s) and provide a detailed explanation as to where your trouble with the problem is and it will be much easier to help.
• Feb 11th 2009, 01:31 PM
Stillen GLE
Quote:

Originally Posted by TheMasterMind
Post a specific problem(s) and provide a detailed explanation as to where your trouble with the problem is and it will be much easier to help.

when the number is a 3 digit number up top and bottom

345
678

I can go do 5x8 4x8 and 3x8 with no problem but then when I have to start with 5x7 4x6 etc then I get lost.
• Feb 11th 2009, 01:40 PM
TheMasterMind
Quote:

Originally Posted by Stillen GLE
when the number is a 3 digit number up top and bottom

345
678

I can go do 5x8 4x8 and 3x8 with no problem but then when I have to start with 5x7 4x6 etc then I get lost.

This is hard to explain the long way but why don't you check this out Maths Online - Online solutions for Long Multiplication It provides a good explanation and takes you through step by step. (click the next-step button)
• Feb 11th 2009, 01:57 PM
Stillen GLE
Quote:

Originally Posted by TheMasterMind
This is hard to explain the long way but why don't you check this out Maths Online - Online solutions for Long Multiplication It provides a good explanation and takes you through step by step. (click the next-step button)

thanks, I was just using those numbers as an example.
• Feb 12th 2009, 03:42 PM
HallsofIvy
Quote:

Originally Posted by Stillen GLE
when the number is a 3 digit number up top and bottom

345
678

I can go do 5x8 4x8 and 3x8 with no problem but then when I have to start with 5x7 4x6 etc then I get lost.

8*5= 40 so write down the 0 and carry 4.
8*4= 32 so add the carried 4 to 32 to get 35, write down the 6 and carry the 3.
8*3= 24 so add the carried 3 to 24, write down 27
Your first row is 2760, the product of 8 with 345.
At this point you should have
_543
_678
2760

Now, write a 0 under that first 0 to represent "moving over one place" and do the same thing with the second number, 7:
7*5= 35 so write down the 5 and carry the 3.
7*4= 28 so add the carried 3 to 28 to get 31, write down the 1 and carry the 3.
7*3= 21 so add the carried 3 to 21 to get 24 and write down 24
At this point you should have
__543
__678
_2760
24150

Write down two 0s below the last "50" to represent shifting againeo the same thing with the third number, 6:
6*5= 30 so write down the 0 and carry the 3.
6*4= 24 so add the carried 3 to 24 to get 27 write down the 7 and carry the 2.
6*3= 18 so add the carried 2 to the 18 to get 20 and write down 20
The third row is 2070 but again shifted one place to the left.
Now you have
___543
__678
__2760
_24150
203000

I put in those dashes to make everything line up correctly.
• Feb 16th 2009, 02:31 PM
wytiaz
The basic idea is that multiplying 345 by 678 all at once is too much to handle.

So instead, we multiply 345 by (600 + 70 + 8).

So we'll multiply 345 x 600, 345 x 70, and 345 x 8 separately.