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The number of bacteria in a petri dish is multiplied by a factor of 1.2 every hour. There were initially 500 bacteria.
Which expression gives the number of bacteria after 3 hours?
Choose 1 answer:
(A) 
500+1.2*1.2*1.2
(B) 
500*1.2*1.2*1.2
(C) 
500+1.2+1.2+1.2
(D) 
500*(1.2+1.2+1.2)

The number of bacteria in a petri dish is multiplied by a factor of 11.22 every hour. There were initially 500500 bacteria.\newlineWhich expression gives the number of bacteria after 33 hours?\newlineChoose 11 answer:\newline(A) 500+1.21.21.2 500+1.2 \cdot 1.2 \cdot 1.2 \newline(B) 5001.21.21.2 500 \cdot 1.2 \cdot 1.2 \cdot 1.2 \newline(C) 500+1.2+1.2+1.2 500+1.2+1.2+1.2 \newline(D) 500(1.2+1.2+1.2) 500 \cdot(1.2+1.2+1.2)

Full solution

Q. The number of bacteria in a petri dish is multiplied by a factor of 11.22 every hour. There were initially 500500 bacteria.\newlineWhich expression gives the number of bacteria after 33 hours?\newlineChoose 11 answer:\newline(A) 500+1.21.21.2 500+1.2 \cdot 1.2 \cdot 1.2 \newline(B) 5001.21.21.2 500 \cdot 1.2 \cdot 1.2 \cdot 1.2 \newline(C) 500+1.2+1.2+1.2 500+1.2+1.2+1.2 \newline(D) 500(1.2+1.2+1.2) 500 \cdot(1.2+1.2+1.2)
  1. Identify initial data: Identify the initial number of bacteria and the growth factor per hour.\newlineInitial number of bacteria = 500500\newlineGrowth factor per hour = 1.21.2
  2. Understand exponential growth: Understand that the growth of bacteria is exponential, meaning the bacteria are multiplied by the growth factor every hour.
  3. Calculate after 11 hour: Calculate the number of bacteria after 11 hour.\newlineAfter 11 hour: 500×1.2500 \times 1.2
  4. Calculate after 22 hours: Calculate the number of bacteria after 22 hours.\newlineAfter 22 hours: (500×1.2)×1.2=500×(1.2)2(500 \times 1.2) \times 1.2 = 500 \times (1.2)^2
  5. Calculate after 33 hours: Calculate the number of bacteria after 33 hours.\newlineAfter 33 hours: 500×(1.2)2500 \times (1.2)^2 \times 11.22 = 500×(1.2)3500 \times (1.2)^3
  6. Identify correct expression: Identify the correct expression from the given options that matches the calculation for the number of bacteria after 33 hours.\newlineThe correct expression is (B) 500×1.2×1.2×1.2500 \times 1.2 \times 1.2 \times 1.2

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