Question

find the ratio of the circumsfances of twocircles whose radii are in the ratio 4:5​

Answer 1

≡QUESTION≡

Find the ratio of the circumferences of two circles whose radii are in the ratio 4:5​.

║⊕ANSWER⊕║

Let radius of circles be x

Radius of first circle= 4x

Radius of second circle= 5x

Circumference of circle= 2πr

Circumference of first circle= 2×π×4x

Circumference of second circle= 2×π×5x

Ratio of the circumferences= Circumference of first circle/Circumference of second circle

                                               = 2×π×4x/2×π×5x

                                                 = 4x/5x

                                                 = 4/5

                                                 = 4:5

∴The required ratio is 4:5

Answer 2

Let radius of circles = x

We will take a radius first , as it is necessary for us to know radius first .

Radius of first circle= 4x

Radius of second circle= 5x

As we all know ,

Circumference of circle= 2πr

Circumference of first circle= 2×π×4x

Circumference of second circle= 2×π×5x

Ratio of the circumferences= Circumference of first circle/Circumference of second circle

= 2×π×4x/2×π×5x

= 4x/5x

= 4/5

= 4:5 ✓