- #1
TinyTex
- 7
- 0
a digital clock shows the time from 00:00 to 23:59 as a string of four digits
1) how many contain for different strings 4 values e.g. 02:43
i got is as 290 don't think its right
since there are
01,02,03,04,05,06,07,08,09,12 = 10
then there are
22,23,24,25,26,27,28,29,32,34,35,36,37,38,39,42,43,45,46,47,48,49,52,53,54,56,57,58,59
= 29
29x10=290
2) How many contain 3 of the same digit
00: 01,02,03,04,05,06,07,08,09,10,20,30,40,50 =14
11: 01,12,13,14,15,16,17,18,19,21,31,41,51 =13
01,02,03,04,05, : 00,00,00,00,00,00,11,22,33,44,55, =10
06,07,09, : 00,00,00 = 3
14+13+10+3= 40?
12
1) how many contain for different strings 4 values e.g. 02:43
i got is as 290 don't think its right
since there are
01,02,03,04,05,06,07,08,09,12 = 10
then there are
22,23,24,25,26,27,28,29,32,34,35,36,37,38,39,42,43,45,46,47,48,49,52,53,54,56,57,58,59
= 29
29x10=290
2) How many contain 3 of the same digit
00: 01,02,03,04,05,06,07,08,09,10,20,30,40,50 =14
11: 01,12,13,14,15,16,17,18,19,21,31,41,51 =13
01,02,03,04,05, : 00,00,00,00,00,00,11,22,33,44,55, =10
06,07,09, : 00,00,00 = 3
14+13+10+3= 40?
12