NECO 2022 · Paper 1 · Q5

Simplify $2\sqrt{18} - 4\sqrt{32} + 3\sqrt{50}$ .

Worked solution (try it first)

Take out the largest square factor of each: $\sqrt{18} = 3\sqrt{2}$ , $\sqrt{32} = 4\sqrt{2}$ and $\sqrt{50} = 5\sqrt{2}$ .
Multiply by the numbers in front: $6\sqrt{2} - 16\sqrt{2} + 15\sqrt{2}$ .
Collect the like surds: $6 - 16 + 15 = 5$ , so the answer is $5\sqrt{2}$ , option C.