The ratio of the area of the smaller triangle to the bigger triangle is 1 : 4.

Why this happens (quick idea)

If every side of a triangle is doubled, all its linear dimensions (including height) are doubled. The area of a triangle depends on the product of two lengths (like base and height), so when each length is doubled, the area becomes 2×2=42\times 2=42×2=4 times larger.

So:

  • Area of smaller triangle = AAA
  • Area of bigger triangle = 4A4A4A

Therefore,
Area(small) : Area(big) = 1 : 4.

TL;DR: When the sides are doubled, the area becomes four times, so the required ratio is 1:4.