The count of bacteria in a culture grows by 10% during first hour, decreases by 8% during second hour and again increases by 12% during third hour. If the count of bacteria in the sample is 13125000, what will be the count of bacteria after 3 hours?

Given,

P = 13125000

r₁ = 10%

r₂ = 8%

r₃ = 12%

$\therefore \text{Count of bacteria after 3 years} = 13125000 \times \Big(1 + \dfrac{10}{100}\Big) \times \Big(1 - \dfrac{8}{100}\Big) \times \Big(1 + \dfrac{12}{100}\Big) \\[1em] = 13125000 \times \Big(\dfrac{100 + 10}{100}\Big) \times \Big(\dfrac{100 - 8}{100}\Big) \times \Big(\dfrac{100 + 12}{100}\Big) \\[1em] = 13125000 \times \Big(\dfrac{110}{100}\Big) \times \Big(\dfrac{92}{100}\Big) \times \Big(\dfrac{112}{100}\Big) \\[1em] = 13125000 \times \Big(\dfrac{11}{10}\Big) \times \Big(\dfrac{23}{25}\Big) \times \Big(\dfrac{28}{25}\Big) \\[1em] = \dfrac{13125000 \times 11 \times 23 \times 28}{10 \times 25 \times 25} \\[1em] = 14876400$

Hence, the count of bacteria after 3 hours = 14876400.