Data sufficiency QS

[silambarasan.s]

A scientist is studying bacteria whose cell population doubles at constant intervals, at which times each cell in the population divides simultaneously. Four hours from now, immediately after the population doubles, the scientist will destroy the entire sample. How many cells will the population contain when the bacteria is destroyed?

(1) The population just divided and, since the population divided two hours ago, the population has quadrupled, increasing by 3,750 cells.

(2) The population will double to 40,000 cells with one hour remaining until the scientist destroys the sample.

please post ur answers with explanations

[silambarasan.s]

ANS for this problem is A

My answer was D
1.since the population quadrupled in 2 hours it is evident that it is doubling every hour so choice a is correct
2.The population will double to 40,000 cells with one hour remaining until the scientist destroys the sample
and also the question states
"Four hours from now, immediately after the population doubles, the scientist will destroy the entire sample"

as the population doubled one hour prior to the destroyal it is obvious to me from choice 2 that it is doubling every hour

so I chose D.But the answer is given as A can u please explain

[Ben Ku]

To answer the question in this problem, we need to know two things:
(a) How long it takes for the population to double, and
(b) The population of the sample at some given time.

Statement (1) tells us (a) it took the population to double after one hour (since it quadrupled after two hours), and (b) if it quadrupled, increasing by 3750 cells, it means that this is three times as many cells as it had two hours ago. Let's make a chart
Two Hours ago --> 1250
One hour ago --> 2500
NOW --> 5000
Because we know it doubles every hour and we know the population at a given time, Statement (1) is sufficient.

Statement (2) gives the population at a specific time, but it does not tell us how long it takes to double the population. Statement (2) is not sufficient.