Lesson: The Fundamental Counting Principle

Comment on The Fundamental Counting Principle

Thank you. very helpful. Although there are no electric cars with standard transmission. :D
greenlight-admin's picture

Good point about electric cars not having standard transmission!

This is the same diagram we used in Genetics when we constructed different crosses. Thanks so much, very helpful!!
greenlight-admin's picture

Very interesting!

Source: Princeton review cracking the gre 2nd edition

Sandy has a husband and 2 children. She takes at
least 1 member of her family to a diner for lunch
every day. The diner offers 10 lunch specials. If no
one orders the same thing, how many different orders
can Sandy's family make for lunch?

Correct answer choices are 45, 90 and 720

I tried to solve this through the fundamental counting principle. I got 90 and 720 correct by multiplying 10*9 and 10*9*8. I wonder how the question reaches the 45 answer? I understand this can be solved through a combination formula, but I would like to solve it through fundamental counting. Can you help?
greenlight-admin's picture

This is a VERY poorly-worded question.

To begin, what constitutes ONE "lunch order"?
For example, if Sandy orders pasta and her husband orders steak, is that considered different from Sandy ordering steak and her husband ordering pasta? Or is it just considered ONE order of steak and pasta?
The answer choice of 45 suggests that it's considered ONE order of steak and pasta.
However, the answer choice of 720 suggests that this is NOT considered one order (with 3 people).

I suggest that you ignore this question.



why didnt we consider ones digit?

greenlight-admin's picture

Question link: https://greprepclub.com/forum/gre-math-challenge-9-a-palindrome-is-a-num...

Good question! I didn't explain myself very well.
In order for the resulting integer to be a palindrome, the units digit must be the SAME as the hundreds digit.

I've edited my response accordingly: https://greprepclub.com/forum/gre-math-challenge-9-a-palindrome-is-a-num...


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