Trap One: the Height That Escapes the Triangle
When a triangle leans right over — a long, lazy obtuse one — the straight-up height doesn't land inside it anymore. The top corner is hanging out past the end of the base, so the perpendicular drops down outside the shape entirely.
This looks wrong the first time, and people panic and measure the slanted side instead. Don't. The rule hasn't changed one bit: the height is still just how far the top point sits above the base line. We simply stretch the base out with an imaginary dashed line until the height can reach it. Drag the apex way off to the side in the toy and watch the orange line do exactly that.
Trap Two: Which Side Is the Base?
A triangle has three sides, so it has three possible bases — and each one comes with its own height. That sounds like three different answers waiting to happen. Here's the lovely part: you get the same area whichever side you choose.
Flip between “Base = AB”, “BC” and “CA” in the toy. The base and height numbers change every time, but the area stays put. That's your built-in safety check: if a question gives you one base but it's awkward, swap to a friendlier side and you'll still get the right answer.
And the Quiet One: Mixed Units
If the base is in metres and the height is in centimetres, you can't just multiply them. Convert one first so they match, then apply the formula. It's not hard — it's just easy to forget in the rush.