At the start there is a 4/20 (1/5) chance of drawing a blue marble. After putting the marble back in the bag, there is again a 1/5 chance of drawing a blue marble again. To calculate the overall probability, you must multiply the two numbers together: 1/5 x 1/5 = 1/25.
Hi! so you didn’t let us know which side length is missing and it kind of matters so i’ll attach an image so you can just copy the one that looks most like yours.
