Question 187 Data Sufficiency 2018 GMAT Quantitative Review

Question 187 Data Sufficiency 2018 GMAT Quantitative Review

Video explanation[PQID: DS15349]: How many hours would it take Pump A and Pump B working…

Comments

Yinansays

Hi Mr. Dabral,

Can you please help me to clarify my doubt?

Since we know from (1) the rate and from (2) the rate we can find the total time by adding the two rates and find the reciprocal of the result. Why we can’t do that?

From statement 2 alone we can’t compute the time it will take for the Pump B to empty the entire tank. This is because the rate is given in liters per minute, but we don’t know anything about the capacity of the tank. If we knew the volume of the tank in liters, then yes the two statements together would be sufficient.

Another way to think about this is that if Statement 1 gave us the rate of Pump B as 48 (for example) liters per minute and Statement 2 gave the rate as 72 liters per minute, then in this situation the combined rate would be 120 liters per minute, but then we won’t be able to compute the time to empty the tank, because we have no information about the volume of the tank.

Yinan says

Hi Mr. Dabral,

Can you please help me to clarify my doubt?

Since we know from (1) the rate and from (2) the rate we can find the total time by adding the two rates and find the reciprocal of the result. Why we can’t do that?

GMAT Quantum says

Hi Yinan,

From statement 2 alone we can’t compute the time it will take for the Pump B to empty the entire tank. This is because the rate is given in liters per minute, but we don’t know anything about the capacity of the tank. If we knew the volume of the tank in liters, then yes the two statements together would be sufficient.

Another way to think about this is that if Statement 1 gave us the rate of Pump B as 48 (for example) liters per minute and Statement 2 gave the rate as 72 liters per minute, then in this situation the combined rate would be 120 liters per minute, but then we won’t be able to compute the time to empty the tank, because we have no information about the volume of the tank.

I hope this makes sense.

Dabral