Question

diameter of two circles are 15 cm and 25 CM respectively what is the ratio of their circumference

Answer 1

diameter of first circle d1 = 15 cm

radius r1 = d1 ÷ 2 = 15 ÷2 = 7.5 cm

circumference1 = 2πr1

= (2 × 22 × 7.5) ÷ 7 = 330 / 7 cm

diameter of second circle d2 = 25 cm

radius r2 = d2 ÷ 2 = 25 ÷ 2 = 12.5 cm

circumference2 = 2πr2

=( 2 × 22 × 12.5) / 7 = 550 / 7

Find the ratio:
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circumference1 : circumference2

= (330/ 7) : ( 550 / 7)

= 330 : 550 = 3 : 5

Answer: required ratio = 3:5
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Answer 2

diameter = radius / 2
so r = 15/2 cm
and R = 25/2 cm

circumference of first circle = 2pie r
= 2×pie × 15/2
2nd circles circumference = 2×pie× 25/2

Ratio of circumference= (2×pie×15/2) : (2×pie×25/2)
15/2 : 25/2
15 : 25
ratio is 3 : 5
hope it helps...