Question

At an appliance store, if 63 stereos were sold during a one-month period, which of the following must be true?A. At least one stereo was sold on each day of the monthB. Exactly two stereos were sold on the same day during the monthC. At least one stereo was sold on either Monday, Wednesday, or Friday during the monthD. At least three stereos were sold on one day of the month.

Answer 1

Alternative D. At least three stereos were sold on one day of the month.

Explanation:

Now, let's evaluate the options:

A. At least one stereo was sold on each day of the month

It is false.

We can not affirm that. For example, all the stereos can be sold on only one day of the month

B. Exactly two stereos were sold on the same day during the month

It is false.

Same explanation as A.

C. At least one stereo was sold on either Monday, Wednesday, or Friday during the month

It is false.

We can not affirm that too. The explanation is the same as for alternative A.

D. At least three stereos were sold on one day of the month.

It is true.

If two stereos are sold every day, for a month of 30 days, 60 stereos are sold. So, on some days 3 or more stereos are sold.

Also, if all the stereos are sold on the same day, more than 3 stereos were also sold.

So, alternative D is correct.