The question is attached. Please send the step by step complete solution. I also request that please don't send any weblink to this question because I am unable to open thelink everytime.

Asked by sudhanshubhushanroy | 12th Dec, 2017, 08:20: PM

Expert Answer:

begin mathsize 16px style We space have space to space form space 4 minus digit space number.
1 st space digit space can space be space selected space in space 5 space ways.
Similarly comma space 2 nd. space 3 rd space and space 4 th space digits space can space be space also space selected space in space 5 space ways space each.
So comma space total space number space of space ways equals 5 cross times 5 cross times 5 cross times 5 equals 5 to the power of 4 equals 625

Now comma space the space number space of space ways space in space which space straight a space 4 minus digit space number space can space be space formed space
so space that space no space two space digits space are space identical space are space as space follows colon
1 st space digit space can space be space selected space in space 5 space ways
2 nd space digit space can space be space selected space in space 4 space ways
3 rd space digit space can space be space selected space in space 3 space ways
4 th space digit space can space be space selected space in space 2 space ways
rightwards double arrow Total space number space of space ways equals 5 cross times 4 cross times 3 cross times 2 equals 120

Hence comma space required space number equals 625 minus 120 equals 505 end style

Answered by Rashmi Khot | 13th Dec, 2017, 09:48: AM