**NCERT Solution For Class 9, Maths, Chapter 13, Surface Areas And Volumes, Exercise 13.3,** is the very imported exercise for students of class 9 maths. This exercise 13.3, Chapter 13, class 9 basically involves study of Curved surface area of cone and their day to day examples. Class 9, maths chapter 13, ex 13.3 solutions are given below.

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Toggle## Class 9, Maths, Chapter 13, Exercise 13.3 Solutions (Page no. 221)

**Q.1. Diameter of the base of a cone is 10.5 cm and its slant height is 10 cm. Find its curved ****surface area.**

**Ans:** Here, r = $\frac{10.5}{2}$ = 5.25 cm and l = 10.

Curved surface area of the cone = (πrl) cm^{2}

= $\left( \frac{22}{7}\times 5.25\times 10 \right)c{{m}^{2}}$

= 165 cm^{2}

**Q.2. Find the total surface area of a cone, if its slant height is 21 m and diameter of its base ****is 24 m.**

**Ans:** here, $r=\frac{24}{2}=12$ cm and l = 21 m.

Total surface area of the cone = (πrl + πr^{2}) m^{2}

= πr (l + r) m^{2}

= $\frac{22}{7}\times 12\times (21+12)\,{{m}^{2}}$

= $\frac{22}{7}\times 12\times 33\,{{m}^{2}}$

= 1244.57 m^{2} (approx.)

**Q.3. Curved surface area of a cone is 308 cm ^{2} and its slant height is 14 cm. Find**

**(i) radius of the base and (ii) total surface area of the cone.**

**Ans: **(i) Curved surface of a cone = 308 cm^{2}

Slant height, l = 14 cm

Let r be the radius of the base.

∴ πrl = 308

⟹ $\frac{22}{7}\times r\times 14=308$

⟹ $r=\frac{308\times 7}{22\times 14}=7$

Thus, the radius of the base = 7 cm

(ii) Total surface area of the cone = πr(l + r)

⟹ $\frac{22}{7}\times 7\times (14+7)c{{m}^{2}}$

⟹ (22×21) cm^{2}

⟹ 462 cm^{2}

**Q.4. 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 ****₹****70.**

**Ans:**

**Q.5. What length of tarpaulin 3 m wide will be required to make conical tent of height 8 m ****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 π = 3.14).**

**Ans:**

**Q.6. The slant height and base diameter of a conical tomb are 25 m and 14 m respectively. ****Find the cost of white-washing its curved surface at the rate of ****₹****210 per 100 m ^{2}.**

**Ans:**

**Q.7. A joker’s cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.**

**Ans:**

**Q.8. A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones made of recycled cardboard. Each cone has a base diameter of 40 cm and height 1 m. If the outer side of each of the cones is to be painted and the cost of painting is ****₹****12 per m ^{2}, what will be the cost of painting all these cones? (Use π = 3.14 and take$\sqrt{1.04}=1.02$**

**Ans:**

## NCERT Solutions For Class 9, Maths, Chapter 13, Surface Areas And Volumes (All Exercises)

**Class 9, Maths, Surface Areas And Volumes, Exercise 13.1****Class 9, Maths, Surface Areas And Volumes, Exercise 13.2****Class 9, Maths, Surface Areas And Volumes, Exercise 13.3****Class 9, Maths, Surface Areas And Volumes, Exercise 13.4****Class 9, Maths, Surface Areas And Volumes, Exercise 13.5****Class 9, Maths, Surface Areas And Volumes, Exercise 13.6****Class 9, Maths, Surface Areas And Volumes, Exercise 13.7****Class 9, Maths, Surface Areas And Volumes, Exercise 13.8****Class 9, Maths, Surface Areas And Volumes, Exercise 13.9**