2007-05-17 08:24:55 · 8 answers · asked by Brittany B 2 in Science & Mathematics ➔ Mathematics
7,17,27,37,47,57,67,77,87,97
so 11
2007-05-17 08:27:42 · answer #1 · answered by bruinfan 7 · 0⤊ 2⤋
If the second digit is 7, and the first digit is whatever, we get count ten 7's: 07, 17, 27, 37, 47, 57, 67, 77, 87, 97.
If the first digit is a 7, we count 10 more 7's: 70, 71, 72, 73, 74, 75, 76, 77, 78, 79
Note that 77 is counted twice because it contains two 7's.
10+10 = 20.
So although there are 19 numbers that contain 7's, there are in total 20 sevens that will be passed by along the way.
2007-05-17 08:50:52 · answer #2 · answered by NSurveyor 4 · 1⤊ 0⤋
Well, ignoring the 70s, you get one 7 for each 10 numbers, namely between 1 and 10, 11 and 20, etc. So that is 9.
For the 70s, you get one 7 in the ones place and a 7 in the 10s place 10 times. So 11 more for a total of 20.
2007-05-17 09:42:43 · answer #3 · answered by doctor risk 3 · 0⤊ 0⤋
Okay, think logically here. There is one seven for every 10 numbers, right? (like 1, 2, 3, 4, 5, 6, *7*, 8, 9, 10). So for 1-10 there will be 1, 10-20, there will be another one and so on and so forth.
BUT when you hit the 70s there will be a seven in every single one. That's 10 numbers.
So 10+9=19
(The people above me forgot about all the ones in the 70s, don't forget that the first digit of all the 70s is, in fact, 7)
2007-05-17 08:29:00 · answer #4 · answered by Anonymous · 1⤊ 1⤋
11
2007-05-17 08:28:51 · answer #5 · answered by Nicola W 3 · 0⤊ 1⤋
7,17,27,37,47,57,67,77,87,97
70,71,72,73,74,75,76,78,79
i already have 77 on the first line, so im not gonna put it in with second line bcuz might confuse sum people.
i counted 20 seven's
2007-05-17 09:08:34 · answer #6 · answered by $g_monEy$ 2 · 0⤊ 0⤋
If you count the decimals, way too many...;)
2007-05-17 08:33:20 · answer #7 · answered by Jedi squirrels 5 · 0⤊ 1⤋
7,17,27,37,47,57,67,70,71,72,
73,74,75,76,77,78,79,87,97
so 19....
2007-05-17 08:30:42 · answer #8 · answered by Anonymous · 1⤊ 1⤋