In the verge of coronavirus pandemic, we are providing FREE access to our entire Online Curriculum to ensure Learning Doesn't STOP!

# Ex.13.4 Q1 Surface Areas and Volumes Solution - NCERT Maths Class 9

Go back to  'Ex.13.4'

## Question

Assume $$\pi = \frac{{22}}{7}$$ unless stated otherwise

Find the surface area of a sphere of radius:

(i) $$10.5 \rm \, cm$$

(ii) $$5.6 \rm \, cm$$

(iii) $$14 \rm \, cm$$

Video Solution
Surface-Areas-And-Volumes
Ex exercise-13-4 | Question 1

## Text Solution

Reasoning:

Surface area of sphere of radius $$r$$ $$= 4\pi\,\rm{r^2}$$

What is known?

What is unknown?

Surface area of the sphere

Steps:

(i) Radius $$= 10. 5\rm\, cm$$

Surface area of the sphere

\begin{align}&= 4\pi {r^2}\\&= 4 \times \frac{{22}}{7} \times {(10.5)^2} \\&= 1386\,\rm{cm^2} \end{align}

(ii) Radius $$= 5.6\rm\, cm$$

Surface area of the sphere

\begin{align} &= 4\pi {r^2}\\&= 4 \times \frac{{22}}{7} \times {(5.6)^2}\\ &= 394.24\,\rm{cm^2} \end{align}

(iii) Radius $$= 14\rm\, cm$$

Surface area of the sphere

\begin{align} &= 4\pi {r^2} \\&= 4 \times \frac{{22}}{7} \times {(14)^2}\\ &= 2464\,\rm{cm^2} \end{align}

Surface area

\begin{align}&\text{(i) 1386}\,\rm{cm^2}\\&\text{(ii) 394.24}\,\rm{cm^2}\\&\text{(iii) 2464}\,\rm{cm^2} \end{align}

Learn from the best math teachers and top your exams

• Live one on one classroom and doubt clearing
• Practice worksheets in and after class for conceptual clarity
• Personalized curriculum to keep up with school