There are several methods for doing this, but first, you should already be comfortable with adding 2 and 3 digit numbers. Practice this if you don't have confidence in your skill.
In any of these methods, it helps to view the numbers on a grid, starting with the given two numbers each on their own line, just like when doing hand calculations. In the following examples, 'o' is used instead of '0' to represent "floating" numbers, i.e. numbers that have been shifted to the left by a certain number of spaces. The 'o's don't have to be a part of your mental image.
Now as an example, try to multiply these two numbers:
53
29
---
??
If you are comfortable multiplying two-digit numbers by one-digit numbers, then you could do it "textbook style": multiply the first number by the tens and then the ones (or vice verse) of the second number, and add the two results:
__53
x_29
===
_477
106o
===
1537
Most minds find this method too much of a strain, though. A simpler way is to multiply the digits one-by-one, first vertically then diagonally, while keeping a mental running total:
5o x 2o = 10oo (total: 10oo)
__53
__29
===
10oo
3 x 9 = 27 (total: 1027)
__53
__29
===
1027
5o x 9 = 45o (total: 1477)
__53
__29
===
1477
2o x 3 = 6o (total: 1537)
__53
__29
===
1537
Using the running total means that you only need to keep track of 3 or 4 numbers at a time. This fits nicely into a tight square of digits which most people should be able to picture without trouble. You can also do these four digit-by-digit multiplications in any order you choose (just remember to do each of them once!).
Chat with our AI personalities
You multiply the number together - using a calculator if needed.
Basically, it means to add the numbers in your head.
Multiply the numbers together. Double that result. Triple it.
add the number how many times it says
168 = 2 x 2 x 2 x 3 x 7.