Question

A small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is 30 cm long, 25 cm wide and 25 cm high. 

(i) What is the area of the glass? 

(ii) How much of tape is needed for all the 12 edges?

Answer 1

Here, l = 30 cm, b = 25 cm, h = 25 cm. 

(i) Total surface area of the herbarium = 2(lb + bh + hl) 

= 2(30 × 25 + 25 × 25 + 25 × 30) cm² 

= 2(750 + 625 + 750) cm² 

= 2 × 2125 cm² = 4250 cm² 

Hence, area of the glass = 4250 cm² Ans. 

(ii) A cuboid has 12 edges. These consist of 4 lengths, 4 breadths and 4 heights.

∴ length of the tape required = 4l + 4b + 4h 

= (4 × 30 + 4 × 25 + 4 × 25) cm 

= (120 + 100 + 100) cm = 320 cm Ans.