Harrison and Lara's Continuing Adventures

Harrison and Laratwo tireless adventurers who face mathematical roadblocks and puzzles wherever they gohave to use a catapult to fire a large rock over a hill and into a well that they can't see from the catapult's location. They are not permitted to walk anywhere on the hill, so measuring the distance to the well requires a clever plan.

Lara flies a helicopter over the well and drops a rope to measure her height above it. Exactly 125 m of rope is all she needs to touch the well; however, a steady wind is blowing the rope so it makes a straight line at an angle to the ground.

Meanwhile, back at the catapult, Harrison uses a rangefinder to determine that the helicopter is exactly 280 m away from the catapult, at an elevation of 15.

Harrison radios Lara and confirms that the well, the helicopter and the catapult are all in the same vertical plane. Without making any further measurements, he now has enough information to set the distance for the catapult.

Harrison has one critical piece of information that you do not. Without it, you cannot determine the distance to the well with certainty. The information is not a measurementHarrison will have no trouble determining it.

What information does Harrison have that you do not? What are the possible distances to the well? By the end of this module, you should know how to solve this riddle.