BTGmoderatorDC wrote:A biotechnologist started automated half-hourly recording of the conditions of a cell culture at 9 AM on 13 January, 2015. The dial on the recording device moved clockwise through one interval (for example, from A to B) after every 10 recordings. If the dial was at point A at 9 AM on 13 January, 2015, what was the position of the dial, time and date respectively when the 420th recording of the cell culture was taken?


A. B, 3 AM, 21 January, 2015

B. B, 6 AM, 21 January, 2015

C. C, 6 PM, 21 January, 2015

D. C, 3 AM, 22 January, 2015

E. B, 6 AM, 22 January, 2015

OA D

Source: e-GMAT

Looking at the options, it seems that the question is not posted completely. See options C and D. There's a mention of 'C' position on the dial. However, the question narration does not talk about this.

Anyway, we can still get the answer.

So, we have 1 recording = 1/2 hr; thus, 420 recording = 420*1/2 = 210 hours

210 hrs/24 hrs = 8 days and 18 hours

13 January + 8 days and 18 hours = 21 January and 18 hours = 3 am, 22 January, 2015

Only Option D qualifies.

The correct answer: D

Hope this helps!

-Jay
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