Question

Large Small

Blue 17 3
Red 8 12
Find: P(Large or Blue)
Remember to reduce your answer.
Enter

Answer 1

Blue 17 3






This is the rigor answer

Answer 2

7/10

Explanation:

These must be marbles, right? There are 40 marbles all together (add all the numbers in the table).

P(Large or Blue) = P(Large) + P(Blue - P(Large and Blue)

= 25/40 + 20/40 - 17/40

= 28/40

=7/10

Note: P(Large) = 25/40 (the 25 comes from adding numbers in the "Large" column)

P(Blue) = 20/40 (the 20 comes from adding numbers in the "Blue" row)

P(Large and Blue) = 17/40 (that's the number in the Large column AND the Blue row)

The reason for the subtraction is this: if you just add numbers in the Large column and the Blue row, you end up adding the 17 Large AND Blue marbles twice. You want them to be counted only once.