JAMB 1986 · UME · Q44

Solid mensuration

An open rectangular box externally measures $4\text{ m} \times 3\text{ m} \times 4\text{ m}$ (length × width × height). Find the total cost of painting the box externally if it costs ₦2.00 to paint one square metre.

Worked solution (try it first)

The box is open, so paint the base and the four sides but not the top.
Base: $4 \times 3 = 12\text{ m}^2$ .
Sides: $2(4 \times 4) + 2(3 \times 4) = 32 + 24$
$= 56\text{ m}^2$ .
Total $12 + 56 = 68\text{ m}^2$ , and the cost is $68 \times 2 = 136$ , so ₦136.00, option C.

Report a problem with this question