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Mathematics

In a bacteria culture under observation in a laboratory, the population of 50 bacteria doubles itself every hour.

(1) Which of the following expressions gives the bacterial population after n hours ?

  1. 502n\dfrac{50}{2^{n}}

  2. 25n

  3. 50 x 2n

  4. 50n2\dfrac{50^{n}}{2}

(2) The population size of the bacteria after 3 hours will be

  1. 200
  2. 300
  3. 400
  4. 500

(3) How many bacteria will be there in the culture after 1 day ?

  1. 50212\dfrac{50}{2^{12}}

  2. 50 x 224

  3. 50 x 212

  4. 50224\dfrac{50}{2^{24}}

(4) If the culture is observed after every one hour, find the number of hours after which the population size of the bacteria will be larger than 1000.

  1. 5
  2. 6
  3. 8
  4. 10

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Answer

(1) Given:

Initial Population = 50

Growth Rate = Doubles every hour (x2)

The population starts at 50 and multiplies by 2 for every hour.

General formula after n hours:

Population = 50 × 2n

Hence, option 3 is the correct option.

(2) Population size after 3 hours = ?

Population size after n hours = 50 × 2n \quad [From step 1]

By replacing the value of 'n' with 3, we get:

Population size after 3 hours = 50 × 23 = 50 x 8 = 400

Hence, option 3 is the correct option.

(3) Bacteria in the culture after 1 day = ?

We know that 1 day has 24 hours

Population size after n hours = 50 × 2n \quad [From step 1]

By replacing the value of 'n' with 24, we get:

Bacteria in the culture after 1 day = 50 × 224

Hence, option 2 is the correct option.

(4) After how many hours will the population be larger than 1000?

Let's test hours (n):

n = 4: 50 x 24 = 50 x 16 = 800

n = 5: 50 x 25 = 50 x 32 = 1600

Since 1600 > 1000, it happens at 5 hours.

Hence, option 1 is the correct option.

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