Little Pika who is five and half years old has just learnt addition. However, he does not know how to carry. For example, he can add 14 and 5, but he does not know how to add 14 and 7. How many pairs of consecutive integers between 1000 and 2000 (both 1000 and 2000 included) can Little Pika add?
Little Pika is the talking Pikachu in the Detective Pikachu movie. He can add two consecutive numbers between 1000 and 2000 if the first number is of the form 1xyz, with 0<=x<=4, 0<=y<=4, 0<=z<=4. There are 5^3=125 of these numbers. He can also add pairs with the first number of the form 1xy9, with 0<=x<=4, 0<=y<=4. There are 5^2=25 of these numbers. He can also add pairs with the first number of the form 1x99, with 0<=x<=4. There are 5 of these numbers. He can also add 1999+2000=3999. Therefore, the yellow mouse Pokemon can add 125+25+5+1=156 pairs of numbers.
Edited on May 19, 2019, 7:47 pm
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Posted by Math Man
on 2019-05-19 09:18:39 |
Detective Pikachu