Grades 9-10 Video Solutions 2022-2022_9-10

Video Transcription

Question 20. Veronica has 5 rings on her fingers, as shown in the diagram. She takes them off one at a time. In how many different ways can she do this?  To solve this problem, we have to use a factorial. So, we will take the factorial of 5, since there are 5 rings, divided by the factorial of 3, since there are 3 fingers. Factorial  just means that we multiply the number by decreasing consecutive number until we get to 1. So the factorial of 5 is 5 times 4 times 3 times 2 times 1. The factorial of 3 is 3  times 2 times 1. And since we are dividing, we can cross 3 times 2 times 1 from both sides, and we will be left with 5 times 4. So our answer will be B, 20.

Video Summary

Question 20. Veronica has 5 rings on her fingers, as shown in the diagram. She takes them off one at a time. In how many different ways can she do this? To solve this problem, we have to use a factorial. So, we will take the factorial of 5, since there are 5 rings, divided by the factorial of 3, since there are 3 fingers. Factorial just means that we multiply the number by decreasing consecutive number until we get to 1. So the factorial of 5 is 5 times 4 times 3 times 2 times 1. The factorial of 3 is 3 times 2 times 1. And since we are dividing, we can cross 3 times 2 times 1 from both sides, and we will be left with 5 times 4. So our answer will be B, 20.

Keywords

factorial

combinatorics

math problem

rings

permutations