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I came across a question which has different answer than what i believe should be. The questions is as follows:
Certain population of bacteria doubles every 10 minutes. If initial bacteria number is 10^4, whats the final number after 1 hour
Answer given is (2^6)(10^4) , but i think the answer should have been (10^4)^6
Please explain this to me .

mads · Answer

Here Doubles means you should multiply by 2.
So in the first 10 mins it will be  10^4 * 2 
Next 10 mins (After 20 mins from starting point) it will be  (10^4 * 2)*2 
Same way...An hour has six 10 min intervals.
So at the end it is  (10^4 * 2)*2*2*2*2*2 = 10^4 * 2^6

resh · Answer

Initial no of bacteria = 10^4

After 10 mins = 2* (10^4)
After 20 mins = 2* (2* (10^4)) = (2 ^2) * (10^4)
After 30 mins = 2*(2* (2* (10^4))) = (2 ^3) * (10^4)

Similarly, 
After 60 mins = (2^6) * (10^4)

aim730 · Answer

Answer is correct it doubles every 10 mins 
like 2 bact doubles themselves after ten min 2*2 not 2^2 ok......I hope that clears the issue

ezhilkumarank · Answer

There is a formula for this in the MGMAT book.

The final population is given by S * 2 ^ (t/I) where S - initial population, t is the total time and I is the interval at which the population doubles.

Hence final population is

S - 10 ^ 4, t = 60, I = 10
 
= 10 ^ 4 * (2 ^ (60/10))

= 10^4 * 2^6.

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