A street of houses numbered from 1 to 100 inclusive is to be numbered with new brass numerals. How many of the digit "2" would be needed to complete the job?
explain in detail/step by step in how you solved this. thx.
2007-11-19 01:04:17 · 4 answers · asked by dz.dahood 2 in Science & Mathematics ➔ Mathematics
2, 12, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 42, 52, 62, 72, 82 & 92= 20 '2"s are required.
2007-11-19 01:10:51 · answer #1 · answered by Joymash 6 · 0⤊ 0⤋
19
2007-11-19 01:08:26 · answer #2 · answered by karan s 3 · 0⤊ 0⤋
Street numbers (of interest to this question) will be of the form
n2 (there are 10 of them if we include the case where n=0 is a space), and of the form 2n (there are also 10 of them).
The address 22 is counted twice (once in each form) which is OK since it contains the digit '2' twice.
20
Or none, if you are willing to flip the digit 5 around (and install it upside down) to replace missing 2's.
2007-11-19 01:10:02 · answer #3 · answered by Raymond 7 · 0⤊ 0⤋
In each group of 10, there is one number containing a 2 in the one's position, i.e. 2,12,22,32,42,52,62,72,82,92. That is 10.
For the numbers 20-29 (ten numbers) there is also a 2 in the ten's position.
Therefore, 10 + 10 = 20.
2007-11-19 01:13:55 · answer #4 · answered by Anonymous · 0⤊ 0⤋