Multiplying Bacteria

Algebra Level 1

Bacteria is known to multiply very rapidly.

A certain container contains just one bacteria on the first day and there are twice as many on the next day. In this manner the number of bacteria in the container doubles itself everyday.

Assuming that the container would be full of bacteria on the 10th day, on which day would the container be half full?

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9th day 6th day 5th day Not enough information

3 solutions

Mohammad Khaza
Jun 30, 2017

the number gets double every day. so, if today the value is 1. it was (1 x 1/2)=1/2 the day before.

so, if it is full in 10 days. it was half yesterday(in the 9th day)

Nashita Rahman
Jan 23, 2017

Since the number of bacteria doubles each day , the container should be half full on the day before it became full.

It is given that the container was full on day 10 , therefore it was half full on the 9th day.

A Former Brilliant Member
Jan 30, 2017

It is a Geometric Sequence with a common ration of $2$ .

$a_1 = 1$

$a_2 = 2$

$a_3 = 4$

$a_4 = 8$

$a_5 = 16$

$a_6 = 32$

$a_7 = 64$

$a_8 = 128$

$a_9 = 256$

$a_{10} = 512$

Half of $512$ is $256$ , so it will be half full on the ninth day.

Multiplying Bacteria

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