GMAT Absolute Value & Number Line practice questions

A company tracks its daily revenue over a 5-day period. The revenues for the first four days are $120, $150, $130, and $140. The average revenue over the 5-day period must be at least $135. What is the minimum revenue the company must achieve on the fifth day to meet this requirement?

A hotel currently has 60% of its rooms occupied. The ratio of occupied single rooms to occupied double rooms is 3:2. If the hotel has a total of 200 rooms (all either single or double occupancy), and the unoccupied rooms maintain the same single-to-double ratio as the occupied ones, how many single rooms are currently unoccupied?

A library tracks the number of overdue books returned each day. The absolute difference between the number of overdue books returned on Monday and Tuesday is 15. On Wednesday, twice as many overdue books were returned as on Tuesday. If the total number of overdue books returned over these three days is 135, what is the minimum possible number of overdue books returned on Monday? (All quantities must be non-negative integers.)

A power plant tracks its daily energy output using two sensors, A and B, placed at different points in the distribution network. Sensor A records output values between 5 and 50 megawatts $MW$, while sensor B records values between 100 and 1000 MW. Both sensors use the same linear scaling formula to convert raw measurements to displayed values: $\text{Displayed Value} = k \times \text{Raw Reading} + b$. Sensor A shows a reading of 20 MW when the raw measurement is 8 units, and 35 MW when the raw measurement is 14 units. Sensor B uses the same scaling constants $k$ and $b$. If sensor B shows a reading of 550 MW, what is the corresponding raw measurement?

A library tracks the absolute difference between the number of books checked out and checked in each day. Over a 5-day period, the daily absolute differences were 12, 8, 15, 6, and x. If the mean absolute difference for the entire period is exactly 10, what is the absolute difference between x and the median of the 5 differences?