What is the probability that one of the two integers randomly selected from range 20-29 is prime and the other is a multiple of 3?
(The numbers are selected independently of each other, i.e. they can be equal)
I got the answer as 0.06 but im not sure why its wrong.
Probability that one integer is a prime number
prime numbers between 20-29 are 23,29
So probability is 2/10 = 0.2
Multiple of 3
Multiple's of 3 between 20 and 29 are 21,24,27
Probability of choosing one prime and one factor of 3= (probability of choosing prime first and factor of 3 second) + (Probability of choosing factor of 3 first and prime second)
= 2 * 0.2 *0.3 = 0.12
Answer is B
Hope if helps!
you must believe
How to start GMAT preparations?
How to Improve Quant Score?
gmatclub topic tags
Check out my GMAT debrief
Thursdays with Ron link
Looking for a Quant tutor? Check out my post for the same!
Combined Formula Sheet :
Number Properties || Word Problems and PnC || Equations, Inequalities || Geometry
How to Solve :
Statistics || Reflection of a line || Remainder Problems