Question

Practice Set 47
1. Find the total surface area of cubes having the following sides.
(i) 3 cm (ii) 5 cm (iii) 7.2 m (iv) 6.8 m
(v) 5.5 m
2. Find the total surface area of the cuboids of length, breadth and height as given below
(i) 12 cm, 10 cm, 5 cm
(ii) 5 cm, 3.5 cm, 1.4 cm
(ii) 2.5 cm, 2 m, 24 m
(1) 8 m, 5 m, 3.5 m
3. A matchbox is 4 cm long, 2.5 cm broad and 15 cm in height. Its outer sides are to be
covered exactly with craft paper. How much paper will be required to do so ?
4. An open box of length 1.5 m, breadth I m, and height 1 m is to be made for use on
trolley for carrying garden waste. How much sheet metal will be required to make th
box? The inside and outside surface of the box is to be painted with rust proof pai
At a rate of 150 rupees per sqm, how much will it cost to paint the bod!​

Answer 1

Answer:

i. Total surface area of cube = 6l2 = 6 × (3)2 = 6 × 9 = 54 sq. cm. ii. Total surface area of cube = 6l2 = 6 × 52 = 6 × 25 = 150 sq. cm. iii. Total surface area of cube = 6l2 = 6 × (7.2)2 = 6 × 51.84 = 311.04 sq. m. iv. Total surface area of cube = 6l2 = 6 × (6.8)2 = 6 × 46.24 = 277.44 sq. m. v. Total surface area of cube = 6l² = 6 × (5.5)2 = 6 × 30.25 = 181.5 sq. m.Read more on Sarthaks.com - https://www.sarthaks.com/861952/find-the-total-surface-area-of-cubes-having-the-following-sides-i-3-cm-ii-5-cm-iii-7-2-m-iv-6-8-m-v-5

Answer 2

Step-by-step explanation:

1.i. Total surface area of cube = 6l2 = 6 × (3)2 = 6 × 9 = 54 sq. cm. ii. Total surface area of cube = 6l2 = 6 × 52 = 6 × 25 = 150 sq. cm. iii. Total surface area of cube = 6l2 = 6 × (7.2)2 = 6 × 51.84 = 311.04 sq. m. iv. Total surface area of cube = 6l2 = 6 × (6.8)2 = 6 × 46.24 = 277.44 sq. m. v. Total surface area of cube = 6l² = 6 × (5.5)2 = 6 × 30.25 = 181.5 sq. m.Read more on Sarthaks.com - https://www.sarthaks.com/861952/find-the-total-surface-area-of-cubes-having-the-following-sides-i-3-cm-ii-5-cm-iii-7-2-m-iv-6-8-m-v-5

2.(1) length =12 cm breadth =10 cm height =5 cm

TSA=2(lb+bh+lh)=2[12×10+10×5+5×12]

TSA=2[120+50+60]=2×230

[TSA=460cm

2

]

(2) length =5 cm breadth =3.5 cm height =1.4 cm

TSA=2(lb+bh+lh)=2[5×3.5+3.5×14+1.4×5]

TSA=2[17.5+4.90+7.0]=2[29.4]

[TSA=58.8cm

2

]

(3) length =2.5 cm breadth =2 m height =2.4 m

TSA=2(lb+bh+lh)=2[0.025×2+2×2.4+2.4×0.025]

TSA=2[0.05+4.8+0.0600]=2[4.91]

(4) length =8 m breadth =5 m height =3.5 m

TSA=2(lb+bh+lh)=2[8×5+5×3.5+3.5×8]

TSA=2[40+17.5+28.0]=2[85.5]

[TSA=171.0m

2

]

3.Solution. Hence, 39.5 cm2 of the craft paper will be needed to cover the matchbox.

4.Solution. Hence, 6.5 m2 of the sheet will be needed to make the open box. Now, it is given that the inside and the outside surface of the open box is to be painted with rust-proof paint. Hence, it will cost 1950 rupees to paint the open box from inside and outside with rust-proof paint