Question

A square land has length $2\sqrt{10}$ ft. The cost of fencing the land is $ 8/ft. The final cost of fencing the land is .

• A. $64
• B. $\$64\sqrt{10}$
• C. $\$16\sqrt{10}$
• D. $\$8\sqrt{10}$

Answer 1

The correct option is B $\$64\sqrt{10}$

Length of one side of the square land = $2\sqrt{10}$ ft.

You know, perimeter of a square = 4 x length of one side.

∴ Perimeter of the square land = $4\times 2\sqrt{10}=4\times 2\times \sqrt{10}=8\sqrt{10}ft.$

A rational number x An irrational number = Irrational number.

The cost of painting is $ 8/ft.

So, the total cost of painting will be =
$\$8\times 8\sqrt{10}=\$8\times 8\times \sqrt{10}=\$64\sqrt{10}$

∴ Total cost of painting = $\$64\sqrt{10}$
and $\$64\sqrt{10}$ becomes an irrational number.