- 132.73 x 4 = 530.92 = 531 (approx.)
EXERCISE 13.3
22 : 3.14
7,
surface area.
V2.
is 24 m.
4.
(i) radius of the base and (ii) total surface area of the cone.
A conical tent is 10 m high and the radius of its base is 24 m. Find
(i) slant height of the tent.
(ii) cost of the canvas required to make the tent, if the cost of 1 m² canvas is 270.
5. What length of tarpaulin 3 m wide will be required to make conical tent of height 8m
and base radius 6 m? Assume that the extra length of material that will be required for
stitching margins and wastage in cutting is approximately 20 cm (Use n = 3.14).
The slant height and base diameter of a cori
mb are 25 m and 14 m
So, there would be approximately 531 grains of corn on the cob.
M. Diameter of the base of a cone is 10.5 cm and its slant height is 10 cm. Find its curved
Find the total surface area of a cone, if its slant height is 21 m and diameter of its base
3. Curved surface area of a cone is 308 cm2 and its slant height is 14 cm. Find
Answers
4. (i) The slant height, l = r2−h2−−−−−−√
= 242+102−−−−−−−−√ m = 576+100−−−−−−−−√ m = 676−−−√ m = 26m
Thus, the required slant height of the tent is 26 m.
(ii) Curved surface area of the cone = πrl
∴ Area of the canvas required
answer to be continued in pic
5.Here, base radius (r) = 6 m
Height(h) = 8m
∴ Slant height (l) = r2−h2−−−−−−√ = 62−82−−−−−−√ m
= 36+64−−−−−−√ m
= 100−−−√m = 10 m
Now, curved surface area = πrl
= 3.14 x 6 x 10m2
= 314100 x 6 x 10 m2 = 1884 m2
Thus, area of the tarpaulin required to make the tent = 188.4 m2
Let the length of the tarpaulin be L m
Length x Breadth = 188.4
⇒ L x 3 = 188.4 ⇒ L = 188.43 = 62.8
Extra length of tarpaulin required for margins = 20cm = 20100m = 0.2m
Thus, total length of tarpaulin required = 62.8 m + 0.2 m = 63 m
3. (i) Let the radius of the base be ‘r’ cm
∴ πrl = 308 ⇒ 227 x r x 14 = 308
r = 308×722×14 = 7cm
Thus, radius of the cone is 7 cm
(ii) Base area = πr2 = 227 x 72 cm2
= 22 x 7 cm2 = 154 cm2
and curved surface area = 308 cm2 [Given]
∴ Total surface area of the cone
= [Curved surface area] + [Base area] = 308 cm2 + 154 cm2
= 462 cm2
