Question

The ratio of the radii of two circles is 2:3. The diameter of the smaller circle is 15 mm. What is the length of the diameter of the larger circle?

Answer 1

we actaully don't need to convert the diameter to radius
15 is smaller, it is 2 units
larger is 3 units
15/2=7.5
7.5 times 3=22.5

answer is 22.5 mm



if you want to do it the long way
convert to radius
15mm/2=7.5mm, that is smaller radius
7.5/2=x/3
times both sides y 6
22.5=2x
divide both sides by 2
11.25=x

taht is radius
now double it for diameter
11.25*2=22.5

answer is still 22.5mm

Answer 2

2:3 15:x 2/3=15/x 2x=(15*3) ( cross multiply) x=45/2 (divide both sides by2) x=22.5 Answer=22.5mm