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## Comment on

Hummingbird Feeder## hi brent

is there any other way to solve this question ?

## Sorry, but I can't think of

Sorry, but I can't think of an alternate solution offhand.

## how about this?

the volume decreases 1/4 every 6 hours, so the volume every 6 hours is 3/4 of the current volume.

to go back in time, I multiply by the inverse of 3/4 which is 4/3

P+12 = 81/16

P+6 = (81/16) * 4/3 = 27/4

P = (27/4) * 4/3 = 9

P-6 = (9) * 4/3 = 12

## That definitely works - nice

That definitely works - nice job!!

## Brilliant!

## Hi Brent,

Instead of 6 hrs ago i started my calculation from 'now' which i got as 9 (if I compare from your table it's correct)..but then how will i proceed further to calculate for 6 hrs ago.

Please help and let me know if this approach is correct.

## If we start at NOW, we get:

If we start at NOW, we get:

Let V = Volume NOW.

NOW: V

6 hrs from now: (3/4)V

12 hrs from now: (3/4)(3/4)V

So we get: (3/4)(3/4)V = = 81/16

Simplify: (9/16)V = 81/16

Multiply both sides by 16 to get: 9V = 81

Solve: 9

So, the present volume is 9 ounces

To find the volume 6 hours in the FUTURE, we take the present volume and MULTIPLY by 3/4.

To find the volume 6 hours in the PAST, we take the present volume and DIVIDE by 3/4.

So, volume 6 hours ago = 9 ÷ 3/4

9 ÷ 3/4 = 9 x 4/3 = 12

Answer: C

Cheers,

Brent

## To avoid big numbers I

## Very nice!!

Very nice!!

## you know what I do? I did it

(3/4)x*(3/4) = 81/16, x = 9, 0.75x = 9, x = 12

## I'm not sure what those steps

I'm not sure what those steps mean. Do you care to elaborate?

## so 3/4 is 75%, decrease 1/4

## Perfect!

Perfect!