Your age by chocolate math
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Originally Posted by girl_geek /img/forum/go_quote.gif This only works if you are less than 100 years old
Say the number you choose is x. Then after step 5, you always get a number in the form of 2x06 or 2x05:
(x * 2 + 5) * 50 + 1756 = 2x06
or
(x * 2 + 5) * 50 + 1755 = 2x06
For example, if you choose x = 7 and you have already had your birthday, after step 5 you get
(7 * 2 + 5) * 50 + 1756 = 2706
Notice that as long as you subtract any number between 1907 and 2006, you will get a 3-digit number where the first digit is 7. (If you have not had your birthday, then you can subtract any number between 1906 and 2005 to get the right answer.) This should work for any x you choose, though I didn't bother to check it for every possible digit. But for another example, if x = 1, then:
(1 * 2 + 5) * 50 + 1756 = 2106
So again, subtracting a number between 1907 and 2006 will give you 1. So I'm just guessing this works for every x.
This also means that just by changing the number you add in step 6, you can make this puzzle work for any year, not just 2006.
I like math puzzles
Originally Posted by girl_geek /img/forum/go_quote.gif Anyone could do what I did by just picking several different values for the number of days you want chocolate, then just writing down the numbers you get at each step and noticing the pattern.... when I saw the number 2706 pop up when I picked 7 for the first number, it made me think that wasn't just a coincidence
So then I knew that the final answer has to be between 700 and 799, if we want a 3-digit number that begins in 7. So 2706 - 700 = 2006, and 2706 - 799 = 1907, so that means you need to subtract a number between 1907 and 2006 in step 6 to get the right answer.
Girl Geek, I love your post. You remind me of a friend who's a Mensa member. We have very deep conversations.
Great brainteaser!
Say the number you choose is x. Then after step 5, you always get a number in the form of 2x06 or 2x05:
(x * 2 + 5) * 50 + 1756 = 2x06
or
(x * 2 + 5) * 50 + 1755 = 2x06
For example, if you choose x = 7 and you have already had your birthday, after step 5 you get
(7 * 2 + 5) * 50 + 1756 = 2706
Notice that as long as you subtract any number between 1907 and 2006, you will get a 3-digit number where the first digit is 7. (If you have not had your birthday, then you can subtract any number between 1906 and 2005 to get the right answer.) This should work for any x you choose, though I didn't bother to check it for every possible digit. But for another example, if x = 1, then:
(1 * 2 + 5) * 50 + 1756 = 2106
So again, subtracting a number between 1907 and 2006 will give you 1. So I'm just guessing this works for every x.
This also means that just by changing the number you add in step 6, you can make this puzzle work for any year, not just 2006.
I like math puzzles
Originally Posted by girl_geek /img/forum/go_quote.gif Anyone could do what I did by just picking several different values for the number of days you want chocolate, then just writing down the numbers you get at each step and noticing the pattern.... when I saw the number 2706 pop up when I picked 7 for the first number, it made me think that wasn't just a coincidence
So then I knew that the final answer has to be between 700 and 799, if we want a 3-digit number that begins in 7. So 2706 - 700 = 2006, and 2706 - 799 = 1907, so that means you need to subtract a number between 1907 and 2006 in step 6 to get the right answer.
Girl Geek, I love your post. You remind me of a friend who's a Mensa member. We have very deep conversations.
Great brainteaser!
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Originally Posted by speerrituall1 /img/forum/go_quote.gif Girl Geek, I love your post. You remind me of a friend who's a Mensa member. We have very deep conversations.
Great brainteaser!
Wow, that's the first time I've been compared to a Mensa member! lol I did get a second major in math just for fun (it was only 3 extra classes with my Computer Science major, lol), but my IQ is still a ways from genius level!
My brother, on the other hand, has an IQ of 150, which is usually considered the cut-off for genius level
Great brainteaser!
Wow, that's the first time I've been compared to a Mensa member! lol I did get a second major in math just for fun (it was only 3 extra classes with my Computer Science major, lol), but my IQ is still a ways from genius level!
My brother, on the other hand, has an IQ of 150, which is usually considered the cut-off for genius level
