On my calculator screen, the number 2659 can be read upside down as 6952.The digitsthat can be read upside down are 0,1,2,5,6,8,9 and are read as 0.1.2.5.9.8.6 respectively.Starting with 1, the fifth number that can be read upside down is 8 and the fifteenth is 21.What are the last three digits of the 2007th number that can be read upside down?
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1 Answers
62On my calculator screen, the number 2659 can be read upside down as 6952.The digitsthat can be read upside down are 0,1,2,5,6,8,9 and are read as 0.1.2.5.9.8.6 respectively.Starting with 1, the fifth number that can be read upside down is 8 and the fifteenth is 21.What are the last three digits of the 2007th number that can be read upside down?
This is a great question... First find the number of 1 digit numbers that can be read upside down Answer is 6
The number of 2 digit numbers that can be read upside down is 6x7=42
No of 3 digit numbers that can be read upside down is 6x7x7 = 294
No of 4 digit numbers that can be read upside down is 6x7x7x7 = 2058
So we are beyond 2007
now you have to carefully climb down!
Can you do that by some elimination..
(Hint: Do you remember how to find the position of Elephant in all the words that can be made by the letters in Elephant?)