# Thread: Help with multiplying large numbers by hand

1. ## 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.

2. 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.

3. 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.

4. 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)

5. 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.

6. 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.

7. 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.