Multiply two 3 digits numbers in your head
This article will show how to do multiplication of two three digits numbers from right to left. Consider 234 × 456.
Step 1: Multiply the last digits. Write 2, carry 4.
Step 2: Cross multiply the one and the tenth, and add them together. We get 53. Add the 4 that we carry to 53. We get 57. Write 7, carry 5.
Step 3: Multiply all digits, like in the figure below. We get 55. Add the 5 that we carry to 55. We get 60. Write 0, carry 6.
Step 4: Finally, multiply the two left digits. We get 22. Add the 6 that we carry to 22. Write 2, carry 2.
Step 5: Finally, multiply the left digits. Add the 2 that we carry to 8. We get 10. Write both numbers.
Therefore, the answer is 108072.
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Category: Mathematics | Comment (RSS) | Trackback
Kujie:
Terimakasih… berminatnya saya.
saya telah bookmark web ini untuk anak saya
August 18, 2008, 9:07 amselinap.com:
Kujie: Thank for bookmarking.
August 18, 2008, 10:33 amNoktahHitam:
isnt this the same as multiplying using the normal method, only a little fancy.
Not many can calculate this using head. We invented calculators, use it :p
August 18, 2008, 5:16 pmselinap.com:
Actually, it is a bit faster to calculate this way. For instant, if you notice, we no more have the three rows, like normal multiplication of 3×3.
With just a little practice, you could impress others.
Why would you want to do that?
Suppose that you are a marketing executive. It would be great if you could give an instant conclusion for a list of numbers. Isn’t it?
Just my 2 cents.
August 18, 2008, 5:24 pmAdila:
nice! a great tip! why didn’t i come across before?
i took a math module before where no calculators are allowed during the exam LOL
so, my lecturer teached me this way..
i’m using your example btw ^^
237 x 456
make it simpler as :
237 x 400 = 94800 — 1
237 x 50 = 11850 — 2
237 x 6 = 1422 — 3
add all the answers (1 + 2 + 3) together and you’ll get the same answer ^^
it’s one of many ways to make difficult question seems easy
that way helped me a lot since i’m such a careless person when calculating more than 2 digits LOL
do share more math tricks please!
August 20, 2008, 6:46 pmAdilas last blog post..Old Mates II
selinap.com:
Adila: IMHO, this technique is the same as normal multiplication.
What you do is separating the rows, and add zeroes at the back according to one, hundreds and thousands.
In normal multiplication technique, we just add empty spaces instead of zeroes.
BTW, perhaps this technique could be useful for people that cannot see between the lines, as an alternative.
Some people can see clearly from one window, while the others might have seen clearer from the other window.
August 21, 2008, 7:25 am