A school took 225 children on a trip to a theme park.

After the trip the children had to write about their favourite ride at the park from a choice of three.

The table shows the number of children who wrote about each ride.

Ride written about

The Drop

The Beanstalk

The Giant

Total

Year group

Year 7

24

45

23

92

Year 8

36

17

22

75

Year 9

20

13

25

58

Total

80

75

70

225

Three children were randomly selected from those who went on the trip.

Calculate the probability that one wrote about 'The Drop', one wrote about 'The Beanstalk' and one wrote about 'The Giant'.

i do not understand why the porobability is x by 6 at the end