1. p(a) = 0.25\np(b) = 0.20\np(a and b) = 0.40\nwhat is p(a or b)?

Explanation:

Step1: Recall the formula for P(A or B)

$P(A\cup B)=P(A)+P(B)-P(A\cap B)$

Step2: Substitute given values

$P(A) = 0.25$, $P(B)=0.20$, $P(A\cap B)=0.40$. So $P(A\cup B)=0.25 + 0.20-0.40$

Step3: Calculate the result

$P(A\cup B)=0.05$

Answer:

$0.05$