BTGmoderatorLU wrote:Source: Manhattan Prep

What percentage of the current fourth graders at Liberation Elementary School dressed in costume for Halloween for the past two years in a row (both this year and last year)?

1) 60% of the current fourth graders at Liberation Elementary School dressed in costume for Halloween this year.
2) Of the current fourth graders at Liberation Elementary School who did not dress in costume for Halloween this year, 80% did not dress in costume last year.

The OA is E

Let's take each statement one by one.

1) 60% of the current fourth graders at Liberation Elementary School dressed in costume for Halloween this year.

Certainly insufficient.

2) Of the current fourth graders at Liberation Elementary School who did not dress in costume for Halloween this year, 80% did not dress in costume last year.

Certainly insufficient.

(1) and (2) together

Given that 60% of the current fourth graders at Liberation Elementary School dressed in costume for Halloween this year, we have 100% - 60% = 40% of the current fourth graders at Liberation Elementary School who did not dress in costume for Halloween this year.

This means that 80% of 40% = 32% did not dress in costume last year.

However, we do not want the answer for what percentage of the current fourth graders did not dress in costume for Halloween for the past two years in a row. We want an answer for what percentage of the current fourth graders at Liberation Elementary School dressed in costume for Halloween for the past two years in a row; however, it is not answered. Insufficient.

The correct answer: E

Hope this helps!

-Jay
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