Does the probability that you will draw a shape or a purple star involve disjoint or overlapping events? What formula would you use to calculate this probability?

Question

anonymous · Answer

These are the cards I'm supposed to use.

anonymous · Answer

Please help! Will give medal and fan!

phi · Answer

A shape is any thing in the first row
a purple star is the last element in the first row

those events overlap.

anonymous · Answer

Could you explain more? I am still confused!?!

phi · Answer

You have 12 boxes.
4 of the boxes have shapes
the probability of picking a shape is 4/12  or (simplifying) 1/4

phi · Answer

the purple star is a specific shape.

if you picked a purple star you also picked a shape.  That means the events:
"pick a shape"  and "pick a purple star" are not independent.

anonymous · Answer

Okay meaning that they are the same almost

anonymous · Answer

So all together what would my answer be?

phi · Answer

if you circle the events " a shape" you put a circle around the first row

now  circle the event " purple star" 

notice that the circles overlap.  that means the events overlap

phi · Answer

to find the probability of overlapping events A or B use 
Pr( A or B) = Pr(A) + Pr(B) - Pr(A and B)

phi · Answer

The pr of a shape is 4/16 or 1/4

phi · Answer

the Prob of a purple star is 1/16

the prob of a purples star and a shape is still 1/16

so the answer is
1/4 + 1/16 - 1/16 = 1/4