Officer Aptitude Rating (OAR) Complete Practice Test 2025

To determine the effective fill rate with both the filling and emptying pipes open, first, it’s important to assess the rates at which each pipe operates.

When filling the tank, the fill pipe takes 15 minutes to fill it completely. This means that the fill rate is equal to 1 tank per 15 minutes, or 4 tanks per hour, translating into an effective rate in gallons per minute if the tank's total capacity is known.

Conversely, the emptying pipe takes 30 minutes to drain the tank. Thus, its emptying rate is 1 tank per 30 minutes, or 2 tanks per hour. This reflects a draining rate of 2 tanks for every 60 minutes.

To find the effective rate when both pipes are running simultaneously, we take the fill rate and subtract the emptying rate. In terms of tank capacity:

- The fill pipe fills up at a rate of 4 tanks per hour.

- The empty pipe drains at a rate of 2 tanks per hour.

When these rates are combined, you calculate the net rate:

Effective fill rate = Fill rate - Empty rate = 4 tanks/hour - 2 tanks/hour = 2 tanks/hour.

Now, converting this to a per minute basis