A rectangular tabletop is 10 feet long and 4 feet wide. Which calculation correctly finds its area?

$10 \text{ ft} + 4 \text{ ft} = 14 \text{ ft}$

$10 \text{ ft} \times 4 \text{ ft} = 40 \text{ ft}$

$(10 \text{ ft} + 4 \text{ ft}) \times 2 = 28 \text{ ft}$

$10 \text{ ft} \times 4 \text{ ft} = 40 \text{ sq. ft}$

A student calculates the area of a square with 5-meter sides and writes the answer as '25'. What is the error in this answer?

The multiplication is incorrect.

The student should have added the sides.

The answer is missing the square units.