PS question a Day

axefx wrote:

rajs.kumar wrote:PS 007

What is the probability that a card selected from a deck will be either an ace or a spade?
A. 2/52
B. 2/13
C. 7/26
D. 4/13
E. 17/52

Answer is E. 17/52
4 aces and 13 spade cards... this is an OR condition so add the two probabilities:

4/52 + 13/52 = 17/52 !

I'm not so sure your logic here is correct. Imagine a deck of just four cards, an Ace and King of spades, and an Ace and King of clubs. Now, given the same question, "what is the probability of drawing either an ace or a spade?"

By your logic:

Probability of drawing an Ace = 2 / 4 = 1/2.

Probability of drawing a spade = 2 / 4 = 1/2.

Added together, 1/2 + 1/2 is 1. In other words, that says the probability that you will draw either an Ace or a spade is 100%. That clearly CANNOT be the case because I could draw the King of clubs, neither an Ace nor a spade.


I agree with the previous post. You must account for double counting. You have 3 possible cards which satisfy your condition: the two Aces, and the King of spades. Thus, the probability is 3/4.


wlvoh

[the correct answer is 2. It cannot be 3 because 3 and 9 give u 12 and the third term becomes equal to the median 9. therefore when u have 2, the
order is clear viz 2 9 10 and it adds up to 21

ajith wrote:PS001


The cost of picture frame M is $10.00 less than 3 times the cost of picture frame N. If the cost of frame M is $50.00, what is the cost of frame N?

A) $13.33
B) $16.66
C) $20.00
D) $26.66
E) $40.00


Answers in three days of time

How do you know if we should write

M = 3N-10 or M = 10 - 3M ??