Pool losing 2 gallons of water a minute

falcios

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Sep 28, 2016
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17
Question
Jane has 30 gallons in her swimming pool. She pulls the plug and it is losing 2 gallons a minute.
When will she have 5 gallons left?

The answer posted is -2m+30=5


My answer is -2m+32=5

Isn't this a arithmetic sequence related question so the first number in the sequence should be 30; -2(1)+32

Thanks in advance.
 
Question
Jane has 30 gallons in her swimming pool. She pulls the plug and it is losing 2 gallons a minute.
When will she have 5 gallons left?

The answer posted is -2m+30=5


My answer is -2m+32=5

Isn't this a arithmetic sequence related question so the first number in the sequence should be 30; -2(1)+32

Thanks in advance.
Initially 30 gallons
After 1 minute there is 30 -2*1 gallons left (using your formula there is still 30 gallons left)
After 2 minutes there is 30 - 2*2 gallons left
After 3 minutes there is 30 - 2*3 gallons left (do you see a pattern)
,,,,
After m minutes there is 30 - 2*m gallons left

Now the posted answer is obviously wrong as it does not answer the question which is an amount of time, not an equation. You want to lose 25 gallons and you lose 2 gallons per minutes. The answer is 12 1/2minutes. You can solve for m using the formula they gave and you'll get 12 1/2 as well.
 
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Question
Jane has 30 gallons in her swimming pool. She pulls the plug and it is losing 2 gallons a minute.
When will she have 5 gallons left?

The answer posted is -2m+30=5
Well, that's the equation you need to solve. From there, -2m= -30+ 5= -25 so m= 25/2. She will have 5 gallons left after 12 minutes and 30 seconds.


My answer is -2m+32=5
Where did you get the "32"? There is no "32" in the statement of the problem.

Isn't this a arithmetic sequence related question so the first number in the sequence should be 30; -2(1)+32
That would be correct if we were told that the there were 30 gallons in the pool one minute after the draining started. But that is not the statement of the problem. There were 30 gallons before the draining started so at m= 0, not m= 1.

Thanks in advance.
 
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