Activity: Note the frequency of two-wheelers, three-wheelers and four-wheelers going past during a time interval, in front of your school gate. Find the probability that any one vehicle out of the total vehicles you have observed is a two-wheeler.

Lets assume a case:
Number of 2 wheelers passed = 18
Number of 3 wheelers passed = 23
Number of 4 wheelers passed = 19
The time interval is 15 minutes for all the 3 conditions.
Total number of vehicles passed = Number of 2 wheelers + Number of 3 wheelers + Number of 4 wheelers = 18 + 23 + 19 = 60
Probability that one vehicle out of total vehicles is 2 wheelers = 18/60 = 3/10