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?

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

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