Answer the following questions.
(1) As for two digit integers of 10, 11, 12.13, -----, 99, I make make 90 pieces of numbers by multiplying the number of tens digit and ones digit together, respectively.
Find the sum total of 90 numbers.
(2) As for four digit integers of 1000, 1001, 1002.1003, -----, 2013, I make make 1014 pieces of numbers by multiplying the number of thousands digit, hundreds digit, tens digit and ones digit all together, respectively.
Find the sum total of 1014 numbers.
(3) Among 1014 pieces of numbers made at (2), find the number of numbers of which ones digit is 7.
(1) As for two digit integers of 10, 11, 12.13, -----, 99, I make make 90 pieces of numbers by multiplying the number of tens digit and ones digit together, respectively.
Find the sum total of 90 numbers.
(2) As for four digit integers of 1000, 1001, 1002.1003, -----, 2013, I make make 1014 pieces of numbers by multiplying the number of thousands digit, hundreds digit, tens digit and ones digit all together, respectively.
Find the sum total of 1014 numbers.
(3) Among 1014 pieces of numbers made at (2), find the number of numbers of which ones digit is 7.
Answer
(1) 2025
(2) 91125
(3) 16 pieces
(2) 91125
(3) 16 pieces
