Question

A colony of bacteria starts with 9 bacteria at noon. If the number of bacteria triples every 20 minutes, how many bacteria will be present at 2:40 pm that afternoon?

Answer 1

$<i>Heya !$

Here's your answer !!

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▶Colony of bacteria starts with 9 bacteria at noon , that is at 12 PM.

▶No. of bacteria triples every 20 mins

Therefore ,

How many bacteria will be present at 2:40 pm that afternoon?

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SOLUTION

Time between 12 PM to 2:40 PM =

2 : 40 - 12 : 00

=> 2 : 40 hours

Converting into minutes :

=> 2 × 60 + 40

=> 180 minutes

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Dividing by 20 :

180/20

=> 8 times

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Since the bacteria will triple 8 times till 2 : 40 PM,

THE EQUATION FORMED

=> 9 × 3 × 3 × 3 × 3 × 3 × 3 × 3 × 3

=> 9 × 9 × 9 × 9 × 9

=> 81 × 81 × 9

=> ( 81 )² × 9

=> ( 80 + 1 )² × 9

=> { ( 80 )² + ( 1 )² + 2 ( 81 ) ( 1 ) } × 9

=> 6561 × 9

=> 59, 049 bacteria ANS