Question

The speed of a car is 80 miles per hour. Find the radius of the car wheels in inches if the car makes 300 rev/min.

Answer 1

I got r=44.82 inches is it correct?

Answer 2

how many revolutions per hour does it make?

Answer 3

5 rev per hour

Answer 4

really? it does 300 revs in one minute; how can it do way less revs in one hour?

Answer 5

300*60 ...

Answer 6

sorry for that I interchanged it :)
18000 per hour

Answer 7

18000 revs in one hour put to the ratio of 80 miles

18000/80 is our next step i believe

Answer 8

of if we knew how many inches 80 miles was we could go more directly to an answer ....

Answer 9

why did you made it into ratio?

Answer 10

becasue that is what it is:

18000 revs = 80 miles

i spose since we want to know how far 1 rev takes us its better to make the rev side equal to 1 tho

divide both sides by 18000

Answer 11

1 rev = the circumference of the wheel

Answer 12

sorry I got confused :)

Answer 13

if we convert 80 miles to inches; then we know how many inches 1 rev is; so we would know how many inches the circumference of the wheel is

knowing circunference is equal to 2pi*radius; we solve for the radius

r = C/2pi

Answer 14

Sorry, but I am really confused with your method. :)
I did angular and linear speed with this one.

Answer 15

google says: 1mile=63360inches

multiply both sides by 80 we get

80 miles = 5 068 800 inches

18000 revs = 5 068 800 inches

divide both sides by 18000 to get 1 revolution

5 068 800/ 18000 = 281.6

281.6 inches is our circumference

therefore, using what i posted up above;

radius = 281.6/(2pi)

Answer 16

i did the same, i converted angular (rpm) into linear (miles, inches)

Answer 17

of course i get about a wheel that is about 7 feet in diameter lol

Answer 18

brb. i'll try to understand your method. it looks good :)
still, I think we got the same answer but different method of getting it.

Answer 19

44.82, yes

Answer 20

and I think your method is faster :)