ISI 2005 Q 9

[Dr. Strange]

Need help :

[Akash]

As each button is pressed once, we have only triplets possible. This is an arrangement of 3 distinct objects taking 3 at a time.
Thus, 3C3*3!=6

But I'm sure that can't have been the answer for you to have asked this question. But, I cant think of any hole in this reasoning. maybe the answer is given wrong?

[varnika1880]

Is the ans 13?

[varnika1880]

I mean if he press 3 buttons simultaneously :1
If 2 buttons then =6 cases
If 1 button at a time = 6cases
Total 13

[Dr. Strange]

Varnika : your answer is correct.Thanks a lot

Akash: Yeah I was not able to understand question properly. Varnika's answer made it clear.

[varnika1880]

:) have u done  peb 2016 ? M having a couple of doubts

[Dr. Strange]

Yes I did. Which question are you talking about?

[varnika1880]

Q :3