Okay.. So, two random numbers, 41 x 31
Multiply the first digits of both numbers and you get 12_ now to figure out the next ones..
Now multiply the last digits from both numbers and get 1 (1x1= 1) and this will be your last digit..
So now we have 12 _ 1
Now multiple the the outer numbers and the inner numbers and get 7..
Answer is 1271
Let's try that again
44 x 52
4 x 5 = 20 and 4 x 2 = 8 and we have
20_8
Multiple the outer and inner digits and add them to get 28
20288 is too big take the 2 and add it to the 20 and get 2288
The higher digits such as 59x93 we will get into another time.. there is a special trick when you add numbers too big..
Let's find out what 21432 x 11 is.. Well, do not do the long way with a bunch of steps.. Your first number will be the 2 and then add like this..
2 + 1 = 3 and 1 + 4 = 5 and 4 + 3 = 7 and 3 + 2 = 5 and the last number will stay so we get
23575
Now multiply any digit number that is in the teens such as 16x12.. Add the 2 to the 16 and get 18 And 6 x 2 is 12.. So we carry the 1 to get 192
You can do it this way with any number in the teens..
Now what is 54 x 66? Well, let's use this method.. 5x6 = 30 and 4x6 = 24
30 _ 24
Multiply the inner and outer digits and add them to get 54.. 305424 is totally not the answer.. add the 5 to the 30 and the 4 to 2 in the 24 and we get 3564 which is the answer.. Let's do that again..
49 x 87
4 x 8 = 32 and 9 x 7 = 63
So are numbers are 32_63
multiply the inner and outer numbers to get 72 + 28 = 100
So we have 3210063.. Add 10 in the 100 to 32 and get 42.. And then 0 + 6 = 6 So your answer is 4263
I didn't get into all the alternative methods.... But, this is an easy way, if you have a pen and paper on you and never have a calculator.. I find these methods easier and I am surprised it is not taught in schools..
Multiply the first digits of both numbers and you get 12_ now to figure out the next ones..
Now multiply the last digits from both numbers and get 1 (1x1= 1) and this will be your last digit..
So now we have 12 _ 1
Now multiple the the outer numbers and the inner numbers and get 7..
Answer is 1271
Let's try that again
44 x 52
4 x 5 = 20 and 4 x 2 = 8 and we have
20_8
Multiple the outer and inner digits and add them to get 28
20288 is too big take the 2 and add it to the 20 and get 2288
The higher digits such as 59x93 we will get into another time.. there is a special trick when you add numbers too big..
Let's find out what 21432 x 11 is.. Well, do not do the long way with a bunch of steps.. Your first number will be the 2 and then add like this..
2 + 1 = 3 and 1 + 4 = 5 and 4 + 3 = 7 and 3 + 2 = 5 and the last number will stay so we get
23575
Now multiply any digit number that is in the teens such as 16x12.. Add the 2 to the 16 and get 18 And 6 x 2 is 12.. So we carry the 1 to get 192
You can do it this way with any number in the teens..
Now what is 54 x 66? Well, let's use this method.. 5x6 = 30 and 4x6 = 24
30 _ 24
Multiply the inner and outer digits and add them to get 54.. 305424 is totally not the answer.. add the 5 to the 30 and the 4 to 2 in the 24 and we get 3564 which is the answer.. Let's do that again..
49 x 87
4 x 8 = 32 and 9 x 7 = 63
So are numbers are 32_63
multiply the inner and outer numbers to get 72 + 28 = 100
So we have 3210063.. Add 10 in the 100 to 32 and get 42.. And then 0 + 6 = 6 So your answer is 4263
I didn't get into all the alternative methods.... But, this is an easy way, if you have a pen and paper on you and never have a calculator.. I find these methods easier and I am surprised it is not taught in schools..