Question

Each participant in a certain study was assigned a sequence of 3 different letters from the set {A, B, C, D, E, F, G, H}. If no sequence was assigned to more than one participant and if 36 of the possible sequences were not assigned, what was the number of participants in the study? (Note, for example, that the sequence A, B, C is different from the sequence C, B, A.)

Answer 1

Answer: 300

Explanation:

Based on the information given in the question, the number of participants in the study will be calculated thus:

The number if letters in the set are 8 from A - H. This means that there are 8 ways to choose 3 letter when the ordering matters.

This will be:

= 8!/(8 - 3)!

= 8 × 7 × 6

= 336

Since 36 sequences were not assigned, therefore the numbers that were assigned will be:

= 336-36

= 300.

There were 300 participants.