Meteorologists track a storm using radar. The radar shows a storm centered 30km west of town. Ninety minutes later, it's 30km north of town. Let the +x-axis point east and the +y-axis north. Assuming the storm moved with constant velocity, find that velocity.

To find the velocity of the storm, we need to calculate the change in its position over time and then divide that by the time elapsed.

Let's break down the problem step by step:

1. Assign coordinates to the initial position of the storm:
- Let's assume the town's current location is at the origin (0, 0).
- Since the storm is centered 30km west of town, we can assign its initial position as (-30, 0).

2. Assign coordinates to the final position of the storm:
- After 90 minutes, the storm is 30km north of town.
- Therefore, its final position can be represented as (0, 30).

3. Calculate the change in position:
- By subtracting the initial position from the final position, we can determine the change in position.
- Δx = final x-coordinate - initial x-coordinate = 0 - (-30) = 30
- Δy = final y-coordinate - initial y-coordinate = 30 - 0 = 30

4. Calculate the time elapsed:
- The problem states that 90 minutes have passed.

5. Find the velocity:
- Velocity is defined as the change in position divided by the time elapsed.
- Velocity in the x-direction: Vx = Δx / time = 30 km / 90 min = 1/3 km/min (east)
- Velocity in the y-direction: Vy = Δy / time = 30 km / 90 min = 1/3 km/min (north)

Therefore, the velocity of the storm is 1/3 km/min east and 1/3 km/min north.