Question

find the area of circle given that
a. radius=20cm
b. diameter=42cm​

Answer 1

Answer:

Given = a. r = 20cm

b. diameter = 42cm

Find = area of circle

Solution ⤵

Area of circle if

A. Radius = 20 cm

\begin{gathered}are a \: of \: circle = \pi \: r {}^{2} \\ = 22 \div 7 \times 20 \times 20 \\ = 22 \times 400 \div 7 \\ = 8800 \div 7 \\ = 1257.14286cm {}^{2} \end{gathered}

areaofcircle=πr

2

=22÷7×20×20

=22×400÷7

=8800÷7

=1257.14286cm

2

Area of circle when r = 20 cm = 1257.14 cm

1257.14cm {}^{2}1257.14cm

2

B. diameter = 42 cm

so, radius = 42 / 2 = 21 cm

\begin{gathered}area \: of \: circle \: = \pi \: r {}^{2} \\ 22 \div 7 \times 21 \times 21 \\ = 22 \times 3 \times 21 \\ = 66 \times 21 \\ = 1386cm {}^{2} \end{gathered}

areaofcircle=πr

2

22÷7×21×21

=22×3×21

=66×21

=1386cm

2

Area of circle when r = 20cm is 1257.14 cm

AND, Area of circle if d = 42cm is 1386cm

Here is ur right answer