Data Sufficiency

BTGmoderatorLU wrote:Source: GMAT Prep

Sofia will attend a sequence of daily training sessions for her job. On the last day of her training sessions, she will attend either 1 session or 2 sessions. On each of the other days of her training sessions, she will attend exactly 2 sessions. At the end of her third day of attending training sessions, how many sessions will Sofia have left to attend?

1) The sequence of training sessions Sofia will attend will last 6 days.
2) There are a total of 11 training sessions in the sequence of training sessions Sofia will attend.

The OA is B.

As per the information:

Say she has 7 days of training sessions:

Thus, the order of the number of sessions would be 2, 2, 2, 2, 2, 2, (1 or 2)

The number of left to be attended at the end of her third day = 2 + 2 + 2 + (1 or 2) = 7 or 8

So, the answer would depend on two information: 1. The total number of days the training ran and 2. The number of sessions Sofia took on the last day

Let's take each statement one by one.

1) The sequence of training sessions Sofia will attend will last 6 days.

The number of left to be attended at the end of her third day = 2 + 2 + (1 or 2) = 5 or 6

No unique answer. Insufficient.

2) There are a total of 11 training sessions in the sequence of training sessions Sofia will attend.

Since the total number of training sessions is 11, an odd number, Sofia must have attended only 1 (odd number) session on the last day.

The number of left to be attended at the end of her third day

= 11 - number of training sessions she attended for 3 days

= 11 - 3*2 = 5. Sufficient.

The correct answer: B

Hope this helps!

-Jay
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