A biotechnologist started automated half-hourly recording of the condi

Question

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

Show Answer

Official Answer

D

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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

MahmoudFawzy · Answer

the given says that :  0.5 hour ≡ 1 recording , and 10 recordings ≡ 1 interval ,
so we can deduce that  10 recordings ≡ 1 interval ≡ 5 hours

then  420 recordings ≡ 42 intervals ≡ 210 hours

the dial has  10  letters, so after each  10  intervals, it will return to its initial position  A ,
then after  42  intervals, it will be on  C  -->  Eliminate (A,B,E)
 
 210  hours represents  8  days and  18  hours,
so  9 am + 18 hours = 24 hours + 3am  -->  Eliminate (C) 
and  13 January + 8 days + 24 hours = 22 January  -->   D

ScottTargetTestPrep · Answer

Solution:

Since 420 recordings were taken and since recordings are taken every 30 minutes, the 420th reading is taken 210 hours after 9 AM on January 13th. Notice that 210 hours = 8 days 18 hours. Notice also that 8 days from 9 AM, January 13th is 9 AM, January 21st. Adding another 18 hours, we arrive at 3 AM, January 22nd. There is only one answer choice with this date and time, so the correct answer is D.

Answer: D

wali786 · Answer

A biotechnologist started automated half-hourly recording of the conditions of a cell culture at 9 AM on 13 January, 2015. This means to me that every half hour timer will check the status of the cell whether it is 1/2 divided , 1/4divided or fully divided. How does this means that cell will divide completely into two in half an hour.

MathRevolution · Answer

From A to A there are 100 recordings. So, for 400 recordings traversing from A to A will be 4 times.

A to B and then B to C = 10 + 10 = 20 mins. Hence, the position of the dial is at C.

As it is half-hour recording hence for 420 recordings: 420 * 0.5 = 210 hours.

=> 8 * 24 = 192 hours and hence 13 Jan + 8 days = 21st Jan.

=> 210 - 192 = 18 hours more will be counted from 9 am (21st Jan)

=> 9 am to 9pm = 12 hours + 9pm to 12 am = 3 hours + 12 am to 3 am = 3 hours: 12 + 3 + 3 = 18

Final: At C, 21st Jan, 3 am

Answer D

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A biotechnologist started automated half-hourly recording of the condi

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