Answer:
1/4 or 0.25
Step-by-step explanation:
The total possibilities of any 7 digit number using 0-9 is :
9×10×10×10×10×10×10=9000000
To work out the total possibilities in this question :
We look at the conditions :
The first digit can only be 5 numbers :
1 , 3 , 5 , 7 , 9
Now we subtract 5 from 9 :
9-5 = 4
Since no repeats for 2 , 3 , 4, 5, 6:
9 , 8 , 7 , 6 , 5,
5 possibilities for the last digit :
Total possibilities for this code :
4 × 9 × 8 × 7 × 6 × 5 × 5 = 302400
If it begins with 5 that is only 1 possibility for the first digit
1 × 9 × 8 × 7 × 6 × 5 × 5 = 75600
Now we make a fraction :
75600÷302400
Dividing top and bottom by 75600 gives you 1/4 or 0.25
Hope this helped and have a good day
