probability Like between 100 and 999 how many no have the probability that they does not contain 7 ? Choose the correct choice from the following answers:
A) 646/900	B) 648/900	C) 649/900	D) 658/900	E) 642/900
There are 900 numbers between 100 and 999.   those that contain 7 are.....   107, 117, 127, ........ -- 10 of these   207, 217, 227, ........ -- 10 of these too   307, 317, 327, .......   ....   9*10 numbers that end in 7.   170, 171, 172, 173, 174, 175, 176, (NOT 177 WE ALREADY COUNTED IT), 178, 179 -- 9 of these   270, 271, 272, 273, 274, 275, 276, (NOT 277 WE ALREADY COUNTED IT), 278, 279 -- 9 of these   ...   and so on   so 9*9 numbers that have a middle digit of 7   and finally   700, 701, 702, 703, 704.................., but NOT   (707, 717, 727,....) or (770, 771, 772, 773, ....)   So that's  (100 - 10 - 9)= 
<gadget id="calculator"> (100 - 10 - 9)</gadget>
<output>81</output>
81 numbers that start with 7.   We had 900 numbers.   N= 900 - 90 - 81 - 81= 
<gadget id="calculator">900 - 90 - 81 - 81</gadget>
<output>648</output>
648   So the probability is  648/900= 
<gadget id="calculator"> 648/900</gadget>
<output>18/25 = around 0.72</output>
0.72   ANSWER:648/900
<result>B</result>
probability Like between 100 and 999 how many no have the probability that they does not contain 7 ?