Intercept theorem

Find a length using parallel lines.

🔍 Step 1 · Understand

First, look at a worked example

Lines (MN) and (BC) are parallel, with M on [AB] and N on [AC]. AM = 4 cm, AB = 8 cm and AN = 3 cm. How long is AC, in cm?

💡 The tip : Intercept theorem: AM/AB = AN/AC.

🤔 Find the answer in your head, then open the solution.

👀 See the solution

Answer: 6

AM/AB = AN/AC, so AC = AN × AB ÷ AM = 3 × 8 ÷ 4 = 6 cm.

10 questions. Take your time, and ask for a hint if you get stuck.