M4maths Previous Puzzles

04 Sep 2015 Probability

A 3 digit number is such that 2 digits of the number are 1 and 2. What is the probability that we would get success in our one trail to guess the number.

OPtion

1) 1/54
2) 1/6
3) 1/9
4) 1/10
5) 1/48
6) 1/50
7) 1/52
8) 1/900
9) 1/450
10)None of these

Solution

Number of method to select 3rd digit = 10
If is 0 then total 3 digit number = 2*2*1 = 4
If it is 1 then total 3 digit number = 3!/2! = 3
Similarly if number is 2
possible number = 3
If selected number is 3 then 3 digit number = 3! = 6
Similar for 4, 5, 6, 7, 8, 9
So total 3 digit number
= 4 + 2*3 + 7*6
= 4+6+42
52
So required probability = 1/52

Correct Option: 7 Best Solution (2)

bhaskar   9 years AGO

12_ ->8
21_ ->8
_12 ->7
_12 ->7
1_2 ->8
2_1 ->8
121
122
211
212
112
221
46+6=52
total 52 possibilities

Like? Yes (21) | No (5)  

amit   9 years AGO

total no. possible without using 0 are 9*3! =48.
3! because arrangements can be possible

in addition to this 4 more no. are possible when we use third no as 0 with having other no. as 1 and 2 respectively

Like? Yes (18) | No (4)