1. First of all, pick the number of times a week that you eat chocolate. This number
must be more than one but less than ten.
2. Multiply this number by 2 (just to be bold).
3. Add 5 (for Sunday).
4. Multiply it by 50.
5. Add 1750.
6. Add the last two digits from the year you last had a birthday. So if your last
birthday was in 2009, add 9, if the your last birthday was in 2011 then add 11.
7. Now subtract the four digit year that you were born (if you remember).
You should now have a three digit number. The first digit will be your original number
(i.e. how many times you eat chocolate each week). The next two digits give your age.
Can you explain why it works?
n
2n
2n+5
50(2n+5)
50(2n+5)+1750
50(2n+5)+1750+(b%100)
50(2n+5)+1750+(b%100)-b
or,
100n+250+1750-b+b%100
n is shifted 2 places to the left (100n)
250+1750=2000
2000-b is the last 2 digits of birth year (as long as you were born after 2000!)
If you were born before 2000, this does not work.
Sure! This mathematical trick works because of the way the steps are designed to manipulate and combine different numbers. Let's break it down step by step:
1. First, you are asked to pick a number representing how many times you eat chocolate in a week, which must be more than one but less than ten. Let's call this number 'x'.
2. The number you picked is then multiplied by 2. This step is just to add some arithmetic fun to the calculation.
3. Next, you add 5 to the result obtained in step 2. This is to account for Sunday, adding a fixed value to the previous result.
4. The number is then multiplied by 50. This step is done to add two zeros at the end of the number, effectively multiplying it by 100.
5. After that, you add 1750 to the result accumulated so far. This step increases the number even more.
6. Now comes the part where the calculation incorporates the last two digits of the year you last had a birthday. Let's call these two digits 'y'. This step is designed to add your age to the final result.
7. Lastly, you subtract your four-digit birth year from the total obtained in the previous steps. This step effectively subtracts your birth year from the previous result, leaving only the last three digits.
The resulting three-digit number corresponds to your original number (x) representing how many times you eat chocolate each week, and the following two digits represent your age (y).
The trick works because each step adds or manipulates the numbers in such a way that the final result incorporates both the original number and your age, using various arithmetic operations.