Question:
Tick (✓) the correct answer:
The area of the cardboard needed to make a box of size 25 cm × 15 cm × 8 cm will be
(a) 390 cm2
(b) 1390 cm2
(c) 2780 cm2
(d) 1000 cm2
Solution:
(b) $1390 \mathrm{~cm}^{2}$
Surface area $=2(25 \times 15+15 \times 8+25 \times 8)=2(375+120+200)=1390 \mathrm{~cm}^{2}$