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How many students are identified to have measles in all at the end of the 6th day of the outbreak?

 May 16, 2018
 #1
avatar+4259 
+1

1st day:8

2nd day: 16

3rd day: 32

4th day:64

5th day:128

6th day: 256

Now, we have 8+16+32+64+128+256.

If we divide each number by 8, we get:

1+2+4+8+16+32=63

But, we have to multiply back again by 8, because we divided by 8.

Thus, the answer is \(63*8=\boxed{504}\)

smileysmiley

.
 May 16, 2018
 #2
avatar+101228 
+1

Thanks, tertre.....

 

Here's the "short way"  to find the sum, S6, at the end of the 6th day....we have that

 

Sum at any time  =  Initial value  [ 1  - r^n ] / [ 1  - r ]

 

The initial value is 8

The common ratio, r  = 2

n = the number of days

 

So we have

 

S6  =  8  [ 1 - 2^6]  / [ 1 - 2 ]   =   504  students

 

 

cool cool cool

 May 17, 2018
 #3
avatar+4259 
+1

Welcome, CPhill! I like your solution!

smileysmiley

tertre  May 17, 2018

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