QR Question

[Dentalkid434]

Hello All,

This may seem like a simple QR question, but for some reason I am having a difficult time with it:

Math Destroyer test 4: q14

A 120 gallon vat has a drain that pumps out liquid at a rate of 8 gallons per minute. If the vat is empty and the drain is open, at what rate, in gallons per hour, must water be pumped in so that the vat fills in exactly one hour?

A. 128
B. 480
C. 600
D. 500
E. 750

Ugh and I just realized that I am still experiencing problems accessing the GC and OC on qvault - this is so annoying!...and qvault still did not respond...First world problems :-/

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[aqz]

One hour = 60 minutes.

To fill 120 gallons in one hour = 120 gallons/60 minutes = 2 gallons/minute.

8 gallons is lost per minute....meaning you have to add 10 gallons/minute to get 2 gallons/minute in the end.

Convert 10 gal/min to gal/hr => 60 mins/hour so multiply 10 by 60 = 600 gal/hour

 

[Troyvdg]

*nvm....someone posted before me haha
D = R x T

you want the answer in gallons per hour so instantly you know you have to convert 8gal/min to gal/h

to do this, multiply by 60 (60 minutes in 1 hour)--> gives you 480, so you are losing 480 gallons per hour and you want to fill 120 gallons in 1 hour. We have two rates working against each other

So going back to D=RT
you know you want to fill 120 gallons

so 120=RT
we know we want to fill it in 1 hour

120=R(1)
and since our rate will simply be the rate we fill subtracted by the rate we are losing water

120 = (R-480)(1)
solve and get 600 gal/h

 

[Dentalkid434]

One hour = 60 minutes.

To fill 120 gallons in one hour = 120 gallons/60 minutes = 2 gallons/minute.

8 gallons is lost per minute....meaning you have to add 10 gallons/minute to get 2 gallons/minute in the end.

Convert 10 gal/min to gal/hr => 60 mins/hour so multiply 10 by 60 = 600 gal/hour

Thanks! Were the QR questions on the real DAT similar to the style of this math destroyer question?

 

[aqz]

There isn't any kind of specific "style" of questions. Math is math, the only "style" is the calculation type.

Just make sure you can do everything math destroyer.

All I can do to help is to show you how I'd do the problem. Usually, the methods I use to solve these problems are fast and efficient, so your best bet is to just familiarize yourself with certain methods to solve certain types of problems.

 

[dl2501]

There isn't any kind of specific "style" of questions. Math is math, the only "style" is the calculation type.

Just make sure you can do everything math destroyer.

All I can do to help is to show you how I'd do the problem. Usually, the methods I use to solve these problems are fast and efficient, so your best bet is to just familiarize yourself with certain methods to solve certain types of problems.

Hey, sorry for being up a late post. For this question, i can't seem to wrap around the concept. I get that you have to convert to hours, so I got 480 gallons per hour. If it is a 120 gallon vat, wouldn't it mean that it can easily fill the 120 gallon vat in the one hour?

@orgoman22

Thank you!

 

[dl2501]

It drains out at a rate of 480gal/hr. What must the rate of filling it up be so that it filled up in one hour? 600gal/hr.
600gal/hr - 480 gal/hr (drained out) = 120 gal/hr (it will fill a 120 gallon vat in one hour).

So to just clarify then, it is kind of like a combined works problem, such that as it is getting filled, it is also draining out?

Thank you so much!

 

[dl2501]

Yup, you can set it up the same way, except it would be 1/A **-** 1/B = 1/T instead of a plus.

Thank you so much, I appreciate the help!