On a train there was 1 first class carriage, 1 buffet carriage and 4 second class carriages. In how many different ways can they be arranged if the second class carriages must be next to each other?
6 ways 1st - BF - 2nd BF - 1st - 2ng 1st - 2nd - BF BF - 2nd - 1st 2nd - 1st - BF 2nd - BF - 1st
A train has 11 passenger carriages. In any three consecutive passenger carriages, there are exactly 99 passengers. If there are 381 passengers in total, how many passengers are in carriage 9?
On every moving railway carriage there are metal parts which are travelling in the opposite direction to the train and others which are travelling at twice the speed of the train. What are they?
How many ways are there to answer a 20-question exam where 15 questions are true-false and 5 questions are multiple choice with 4 choices each?
In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?
If you have sticks which measure 1, 2, 3, 4, 5, 6, 7, 8 and 9 cm (one of each). How many different triangles can you make using three of the sticks?
