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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!!
Hi Brent, not sure I quite
"to go back in time, I multiply by the inverse of 3/4 which is 4/3"
Let's say we want to solve
Let's say we want to solve the equation: (2/3)x = 12
If we multiply both sides by 3/2 (the reciprocal/inverse), we get: (3/2)(2/3)x = 12(3/2)
Simplify: x = 18
Does that help?
Thanks Brent. I understand
4/3 (P+6) = (81/16) * 3/4 * 4/3
4/3 (P+6) = (81/16)
(P+6) = (81/16) * 3/4
I think you're assuming that
I think you're assuming that the letter P here represents some value.
In m4rt14n's solution above, P is the PRESENT time.
Similarly, P+6 represents 6 hours from now (i.e., present time + 6 hours)
P+12 represents 12 hours from now
And P-6 represents 6 hours ago.
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!