Brain Teasers
Can You Find the Number?
Can you find a five digit number that, if you place a 9 at the beginning to make a new number, is four times larger than if you place the 9 at the end instead?
Answer
23076: 923076 / 230769 = 4.Hide Answer Show Answer
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Comments
WHOA! I'd never get that! Great work .
I'd never ever ever get that either
I found this teaser to be easy, but nonetheless still a good teaser. Knowing that the last digit of the multiplicand is 9, and that 9 * 4 = 36, the last digit of the product has to be a 6. That means that 6 is to the left of the 9 in the multiplicand. Continuing this process to the left (and remembering to add any carries) leads to the answer.
i didnt get it till i saw the answer thanks it was kool
good one
I also found the solution easy, but I love the pattern that this problem uses. For "4 times larger" there is a "5 digit number" for 1 thru 9 where in this problem 9 is used (e.g. 8 | 820512/205128=4 and 6 | 615384/153846=4). I wonder if there are other patterns with other multipliers.
It took me a little work 'cause I have a nasty habit of doing things the "long way", but I used close to the methods discussed above!
I think this is really easy and i didnt even have to work it out
thanks for not being rude cow
i wasnt being rude i was telling the truth!
Initially, because I thought this teaser would require trial and error, I had no desire to work it. There isn't much satisfaction in trial and error solutions. But I was pleased to find that reasoning could be used. My method was similar to those already stated in previous comments, starting with the 6 and going from there. Turned out to be fun.
I thought this was a very clever puzzle, and a good application of algebra. You can say:
900000 + x = 4 * (10*x + 9);
900000 + x = 40 * x + 36;
900000 - 36 = 39 * x;
899964 / 39 = x.
Good teaser!
900000 + x = 4 * (10*x + 9);
900000 + x = 40 * x + 36;
900000 - 36 = 39 * x;
899964 / 39 = x.
Good teaser!
tsimkim, exactly how I did it
tsimkin, sorry
I too did it as tsimkin and found the problem quite easy. It never occurred to me to try some of the other techniques people list here since the problem was so simple.
Still a nice teaser.
Still a nice teaser.
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