<u>We are given:</u>
The time-traveller has 79 books, but he can only take 5 books
since we need to find the number of ways he can choose 5 books, we know that the order in which he takes the books does NOT matter
Hence, we will use combination
<u>Finding the number of ways:</u>
Since we will use combination, ₇₉C₅
We know that the formula for combination is (n!) / (r!(n-r)!)
₇₉C₅ = 79! / 5!(74!)
₇₉C₅ = 22,537,515
Therefore, the time traveller can choose 5 books in 22,537,515 different ways
