Question

A plastic box 1.5 m long, 1.25 m wide and 65 cm deep is to be made. It is to be open at the top. Ignoring the thickness of the plastic sheet, determine : 

(i) The area of the sheet required for making the box. 

(ii) The cost of sheet for it, if a sheet measuring 1 m² costs Rs 20.

Answer 1

Here, l = 1.5 m, b = 1.25 m, h = 65 cm = 0.65 m. 

Since the box is open at the top, it has only five faces. 

(i) So, surface area of the box = lb + 2(bh + hl) 

= 1.5 × 1.25 m² + 2 (1.25 × 0.65 + 0.65 × 1.5) m² 

= 1.875 + 2 (1.7875) m² 

= (1.875 + 3.575) m² = 5.45 m² 

Hence, 5.45 m² of sheet is required Ans. 

(ii) Cost of 1 m² of the sheet = Rs 20 

∴ cost of 5.45 m² of the sheet = Rs 20 × 5.45 m² = Rs 109 Ans