Question

2. Find the total surface area of a closed box of wood whose dimensions are 2 m, 1.5 m and 80 cm Pind the
cost of wood used to make it at the rate of 120.55 per m'.​

Answer 1

A N S W E R :

• Length of the box = 2 m
• Breadth of the box = 1.5 m
• Height of the box = 80 cm
• Cost of one m² = Rs. 120.55

★ First of all convert the height of the box from cm to m :

→ Height of the box = 80 cm

→ Height of the box = 80 ÷ 100

→ Height of the box = 0.8 m

Now, Let's find the surface area of a closed box :

➝ TSA of box = 2(Length × Breadth + Breadth × Height + Height × Length)

➝ TSA of box = 2(2 × 1.5 + 1.5 × 0.8 + 0.8 × 2)

➝ TSA of box = 2(3 + 1.2 + 1.6)

➝ TSA of box = 2 × 5.8

➝ TSA of box = 11.6 m²

• Hence,the surface area of a closed box is 11.6 m².

Now,

⇏Cost of 1 m² = Rs. 120.55

⇏Cost of 11.6 m² = Rs. 120.55 × 11.6

⇏Cost of 11.6 m² = Rs. 1,398.38

Formulas related to the cube and cuboid :

• Volume of cuboid = l × b × h
• C.S.A of cuboid = 2(l + b)h
• T.S.A of cuboid = 2(lb + bh + lh)
• C.S.A of cube = 4a²
• T.S.A of cube = 6a²
• Volume of cube = a³

Answer 2

$\huge\fcolorbox{black}{lime}{Answer}$

Total surface area =2(lb+bh+hl)=2{(2×1.5)+(1.5×0.8)+(0.8×2)}=11.6m2

Volume =lbh=0.8×2×1.5=2.4m3

cost=120.55×volume=120.55×2.4=289.32