I know the answer is 20 but i can't figure it out

I know the answer is 20 but i can't figure it out

Combinations with color problems for kids

Pls solve

There are 30 students in a history class. Twenty percent of the students are randomly chosen to participate in a teacher evaluation

Combination problem

A fan of country music plans to make a custom CD with 12 of her 30 favorite songs. How many different combinations of 12 songs are possible? Is it practical to make a different CD for each possible...

If there is small medium and large pizzas (3 sizes) and up to 4 toppings..how many different ways can u order the pizzas

How many ways can 6 balls be put into 4 boxes? What formula is used to solve?

1. A florist sells 5 colors of roses. How many different combinations of 3 different colors are possible?

4 boxes, 10 balls, none of them can be empty. how many combinations are there? How do you find the answer?

You tell the cashier to surprise you with the toppings you get. What is the probability that you get 3 toppings? express your answer as a fraction or a decimal number rounded to four decimal...

Hi! Just as a follow up question that I don't understand (and if someone could explain how this works) 1) There are 2 red and 4 green identical marbles arranged in a line. How many different arrangements...

For a rail network, it is possible to buy only single tickets from any station on the network to any other station on the network. Each ticket shows the name of the station at which the journey starts...

The digits and letters can repeat.

Prove nCr = nCr-1

combinations in math for liberal arts, C(9,6)

please I need help with this question. I need an explanation. 1- In a cribbage game with 2 people, each player is dealt 6 cards to start a round. How many 6-card hands are possible? would...

How many arrangement can be made from letters v,w,x,y,z taking all letters at a time if v must be second and z never be last

Dan is asked to choose one number from 1 to 10 and one letter from the alphabet. What is the number of combinations of one number and one letter that Dan can choose from?

I have 3 variables. One has 5 options, the second has 5 options, the third has 6 options. How many total combinations are possible