From a class of twenty students, how many different ways can the 1, 2, and 3rd students be chosen?

They can be chosen in 6,840 different ways

Step-by-step explanation:

In this question, we are tasked with calculating the number of ways in which the 1st, 2nd and 3rd students can be chosen.

For the first position, we have 20 people vying for the position and we are to select only one for the position.

The number of ways this is achievable is 20C1 ways = 20 ways

For the second position, we are left with 19 students vying for the position and we are to select only one for the position. The number of ways this is possible is 19C1 ways = 19 ways

For the third position, we are left with 18 students vying for the position. The number of ways this is possible is 18C1 ways = 18 ways

Thus, the total number of ways this cane be done is; 20 * 19 * 18 = 6,840 ways