Question

There are 8 red, 5 yellow and 7 green cubes in a box. What is the probability of drawing a yellow cube and then a green cube,  if the first cube is not replaced before the second cube is drawn?

Answer 1

i think thats a 1 in 20th chance

Answer 2

Step 1: find out how many cubes are there in total.
There are 20 cubes total because 8+5+7 = 20

Step 2: find out how many yellow cubes you have.
In this problem you have 5 yellow cubes out of 20 cubes. So you chances of grabbing a yellow cube is 5 out of 20.

Step 3: simplify. You can simplify 5/20 to 1/5. So you have a 1/5 chance of grabbing a yellow cube.

Step 4: now find how many cube are green. You have 7 green cubes. Because you took out one cube and didn't replace it you now have 19 cubes. So you have a 7/19 chance of grabbing a green cube.

Step 5: now multiply 7/19 times 1/5. Please note you can not simplify 7/19 because 7 and 19 are prime numbers.

Answer 7/95 which is roughly around .073 or 7.3%