Length of a side and corresponding altitude of a triangle is doubled. The area of triangle will become :

1. double

2. half

3. four times

4. one-fourth

The area of a triangle is given by:

Area = $\dfrac{1}{2}$ x length x altitude

When the length of the side and the corresponding altitude of the triangle are doubled:

Area₁ = $\dfrac{1}{2}$ x 2 x length x 2 x altitude

= $4 \times \Big( \dfrac{1}{2} \times \text{length} \times \text{altitude} \Big)$

= 4 x Area

Area₁ = 4 x Area

Thus, the new area of triangle becomes four times the original area.

Hence, option 3 is the correct option.