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April 1st, 2008 | #1 |
Senior Member
Join Date: Sep 2005
Posts: 1,498
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Arithmetic Trick
Your kiddies might have fun with this calculation trick:
Is it possible to calculate your age by how often you enjoy eating out? Get ready for a mathematical mind-bender– and don't cheat by scrolling down first! This takes less than a minute. Work it out as you read, either in your head or on a piece of paper. But be sure you don't read the bottom until you've worked it out! 1. First of all, pick the number of times a week that you would like to go out to eat (more than once but less than 10 times) 2. Multiply this number by 2 (just to be bold) 3. Add 5 4. Multiply it by 50 5. If you have already had your birthday this year add 1758 ... If you haven't, add 1757. 6. Now subtract the four digit year that you were born. You should now have a three digit number. The first digit of this was your original number, (i.e., how many times you want to go out to restaurants in a week). The next two numbers are: YOUR AGE! (Oh YES, it is!) This is the only year (2008) the calculation will ever work, so you have less than nine months to spread this around. I guess they tell you to pick the # of times you want to eat in a restaurant just to make it more interesting! At least for children, anyway. Also, they say you can do this only in 2008. Is anybody here energetic enough to figure out if this trick could be carried out for other years simply by adjusting the figures 1757 and 1758? Or do you think the whole trick would have to be reconfigured to make it work in a year other than 2008? |
April 2nd, 2008 | #2 |
Banned
Join Date: Dec 2006
Location: In your head
Posts: 5,325
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(2x + 5)*50 + 1758 - y
i.e. 100x + 250 + (2008 - 250) - y i.e. 100*(no. you eat out) + (current year - birth year) The last term gives your age, and adding a multiple of 100 to it with the first term gives you a number of which the last two digits are your age. So, yes, simply changing the numbers 1757 and 1758 makes it work for other years. Just subtract 250 or 251 from whichever year to get the numbers. |
April 5th, 2008 | #3 |
Senior Member
Join Date: Sep 2005
Posts: 1,498
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Thanks, Sandor, for figuring this out for me. Nice reminder of Grade 9 Algebra, too.
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