Multiplication: Base Method 1

Hello. Today I am going to teach a new two way trick on how to do the Base Method. The Base Method is a way to use bases to multiply numbers. Some people prefer the Rainbow Method over the Base Method, but that is up to you.

Example: 98 x 95

Step 1:  First, find the closest base of the two factors that is higher than the two factors. A base is a number that is either 10 or a power of 10. This includes 100, 1000, 10000, etc because they are all powers of 10. In this case, the closest base of the two factors that is higher than the two factors is 100.

Step 2: Pick one of the factors in the problem. Figure out that factor minus the base you chose in the previous step. Place that number on top of the factor you chose in the beginning of the step.

                                                                                             -5

                                                                     Example: 98 x 95

As you can see, 95 (the factor I chose) - 100 (the base) =-5. Therefore I put that number on top of 97.

Step 3: Repeat Step 2 for the other factor in the problem.

                                                                                     -2       -5

                                                                     Example: 98 x 95

Step 4: Now do something I like to call "cross-adding". It's when you pick any number and add it to whatever is diagonal from it. For example, if you choose 95, you would add -2, because -2 is diagonal of 95, as shown below:

                                                                                    -2     -5

                                                                     Example: 98 x 95

95 is diagonal of -2. 95 +-2 = 93.

That sum of those 2 numbers is the first 2 digits of your answer.

                                                                 

                                                                  -2     -5

                                                  Example: 98 x 95                Answer: 93

Step 5: Pay attention to your base. Count the number of zeros your base has. This tells you how many digits your answer has left.

                                                      Base: 100.                     Answer: 93_ _

Step 6: To figure out the last 2 digits of your answer. Simply multiply the 2 numbers at the top.

                                                                                     -2     -5

                                                                    Example: 98 x 95   

                                                                        -5 x -2 = 10

                                                                     Answer:       9310

The answer is 9310. Hope this helped! If you have any questions, please post a comment below about it. Thanks!