Irrelevant Information

Sometime, a problem may contain information which is either not needed at all to solve the problem, or needed but only if the problem is to be solved in the slowest of ways. Regardless of the case, irrelevant information can be misleading and confusing. If we are able to identify it when choosing a solution strategy, we are one step closer to getting the problem right.

Danny drove to the grocery store and bought several bags of chips. In order to determine the amount of money that he spent at the store, which of the following information do we NOT need?

(A) $\ \$ Number of bags of chips that Danny bought
(B) $\ \$ Make and model of the car that Danny drove
(C) $\ \$ Cost of 1 bag of chips
(D) $\ \$ (A) and (C)
(E) $\ \$ All of (A), (B) and (C)

Correct Answer: B

Solution:

In order to compute the total amount Danny spent in the store, we need to know how many bags of chips he bought, and how much one bag of chips costs. So, we can eliminate choices (A), (C), (D), and (E).

The make and model of the car don't affect the amount Danny spent at the store. So, we don't need this information.

Incorrect Choices:

(A), (C), (D), and (E)
The solution explains how to eliminate these choices.

Leonard drives a total of 500 miles, stopping at 20 gas stations along the way. If he eats at 25 different restaurants and his trip lasts 10 days, what is the average distance (in miles) Leonard travels each day?

(A) 500
(B) 50
(C) 25
(D) 20
(E) 10

Correct answer: B

Solution:

Leonard drives 500 miles in 10 days, hence on average he travels $\frac{500} { 10} = 50$ miles per day.

Incorrect Choices:

(A)
This is the total distance that Leonard drives, and not the average distance per day.

(C)
This is the number of restaurants Leonard visits.

(D)
This is the number of gas stations along the way.

(E)
This is the number of days that he drove, not the average distance per day.