Q. 5. The following table gives the life times of 400 neon lamps:
(ii) How many lamps have a life time of more than 700 hours?
Lamps having life time in the range 700 - 800 = 74
Lamps having life time in the range 800 - 900 = 62
Lamps having life time in the range 900 - 1000 = 48
Lamps having a life time of more than 700 hours = 74 + 62 + 48 = 184.