Marbles and Bags

Two bags contain different numbers of red and blue marbles. A marble is removed from one of the bags. The marble is blue. What is the probability that it was removed from bag A?
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

Problem

Two bags contain different numbers of red and blue marbles. A marble is removed from one of the bags (it is not known from which bag). The marble is blue. What is the probability that it was removed from bag A?

Bag A

2 RED

Image
Marbles and Bags

3 BLUE

Image
Marbles and Bags

Image
Marbles and Bags

Bag B

3 RED

Image
Marbles and Bags

4 BLUE

Image
Marbles and Bags

Image
Marbles and Bags