ISRO has devised a new digital wrist watch for Abhishek, who will be the first human being to spend 3 Mars years on planet Mars. The watch divides one Mars day into 40 hours, each hour into 60minutes and each minute into 60 seconds. Abhishek has the habit of glancing at his watch frequently throughout the day (and night). What is the probability that he will see all the digits reading the same (for example, 1 : 11 ) during any single glance? Assume the watch is set to a 20 hour format HH:MM, where four past four PM is shown as 4:04
Option
(a) 1/120
(b) 1/200
(c) 1/240
(d)1/120000

• is it (b)
  total prob=40*60=2400
  and the events are
  1:11
  2:22
  3:33
  4:44
  5:55
  11:11
  total events occured=6*2=12
  =>prob=12/2400=1/200
• 10 years agoHelpfull: Yes(67) No(9)
• A)1/120
  no.of time he can see is=40*60=2400 (1:00,1:01,...20:59)
  events are=20 (1:11,2:22,3:33,....20:20 bcoz wath is in 20 hrs format)
  total prob = 20/2400
  =1/120
  so option (a)1/120 is correct
  
• 10 years agoHelpfull: Yes(13) No(27)
• it is (b) because total prob is 2*20*60=2400
  and event which will come
  like 111
  222
  333
  444
  555
  1111
  it will come two times in a day
  then total event is 2*6=12
  and now prob is 12/2400=1/200
• 10 years agoHelpfull: Yes(10) No(0)
• 1:11
  2:22
  3:33
  4:44
  5:55
  6:66
  7:77
  8:88
  9:99
  11:11
  =10
  =10/60*40
  =1/240
  
• 10 years agoHelpfull: Yes(7) No(15)
• why not 6*2/(40*60*60)=1/1200
  he can see his watch every second
  d is right ans
• 10 years agoHelpfull: Yes(3) No(1)
• Why are we not considering 0:00 ?
• 10 years agoHelpfull: Yes(3) No(0)
• I think Sreedhar Reddy is correct bcaz he will see the watch when all the digits are same..
• 10 years agoHelpfull: Yes(2) No(2)
• @ shridhr
  wat about 12:12,13:13,14:14,....20:20
• 10 years agoHelpfull: Yes(2) No(7)
• can anyone explain here why 0:00 is not counted ?
• 10 years agoHelpfull: Yes(1) No(0)
• Pravin Kumar is correct.
  
• 10 years agoHelpfull: Yes(0) No(5)
• plz xplain me dis ??
  
• 9 years agoHelpfull: Yes(0) No(1)
• Since 4 past 4PM is also given as 4:04 in HH:MM format, the correct possibilities will be:
  MORNING (AM):
  1:11 , 2:22 , 3:33 , 4:44 , 5:55 , 11:11 .
  EVENING (PM):
  1:11 , 2:22 , 3:33 , 4:44 , 5:55 , 11:11 .
  
  So overall 12 events out of 40*60 possibilities.
  Hence probability = 12/(40*60)
  = 1/200 (b).
• 7 years agoHelpfull: Yes(0) No(0)