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After a special medicine is introduced into a petri dish containing a bacterial culture, the number of bacteria remaining in the dish decreases rapidly.
The population loses 
(1)/(4) of its size every 44 seconds. The number of remaining bacteria can be modeled by a function, 
N, which depends on the amount of time, 
t (in seconds).
Before the medicine was introduced, there were 11,880 bacteria in the Petri dish.
Write a function that models the number of remaining bacteria 
t seconds since the medicine was introduced.

N(t)=◻

After a special medicine is introduced into a petri dish containing a bacterial culture, the number of bacteria remaining in the dish decreases rapidly.\newlineThe population loses 14 \frac{1}{4} of its size every 4444 seconds. The number of remaining bacteria can be modeled by a function, N N , which depends on the amount of time, t t (in seconds).\newlineBefore the medicine was introduced, there were 1111,880880 bacteria in the Petri dish.\newlineWrite a function that models the number of remaining bacteria t t seconds since the medicine was introduced.\newlineN(t)= N(t)=\square

Full solution

Q. After a special medicine is introduced into a petri dish containing a bacterial culture, the number of bacteria remaining in the dish decreases rapidly.\newlineThe population loses 14 \frac{1}{4} of its size every 4444 seconds. The number of remaining bacteria can be modeled by a function, N N , which depends on the amount of time, t t (in seconds).\newlineBefore the medicine was introduced, there were 1111,880880 bacteria in the Petri dish.\newlineWrite a function that models the number of remaining bacteria t t seconds since the medicine was introduced.\newlineN(t)= N(t)=\square
  1. Identify initial amount and rate: Identify the initial amount of bacteria and the rate of decrease.\newlineThe initial amount of bacteria aa is given as 11,88011,880. The bacteria population decreases by 14\frac{1}{4} of its size every 4444 seconds, which means the remaining fraction of the population after each decrease is 34\frac{3}{4} (since 114=341 - \frac{1}{4} = \frac{3}{4}).
  2. Determine decay factor: Determine the decay factor bb. The decay factor bb is the fraction of the population that remains after each time interval. In this case, every 4444 seconds, the population retains 34\frac{3}{4} of its size. Therefore, b=34b = \frac{3}{4}.
  3. Write exponential decay function: Write the exponential decay function.\newlineThe general form of an exponential decay function is N(t)=a(b)tN(t) = a(b)^t, where N(t)N(t) is the number of bacteria at time tt, aa is the initial amount, bb is the decay factor, and tt is the time in the same units as the decay interval. However, since the decay happens every 4444 seconds, we need to adjust the exponent to reflect the number of 4444-second intervals that have passed. This means we divide tt by 4444 to get the number of intervals.
  4. Write final function: Write the final function.\newlineUsing the values from the previous steps, the function that models the number of remaining bacteria tt seconds since the medicine was introduced is:\newlineN(t)=11,880×(34)t44N(t) = 11,880 \times \left(\frac{3}{4}\right)^{\frac{t}{44}}

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