 okay so let's try this one a cyclist rides at an average speed of 24 miles per hour if he wants to ride 195 kilometers how many hours must he ride so what I've done I've set this problem up just like I said I'm all up I put the given numbers over here on the left the rate at 25 miles per hour and hopefully you can see by now that that's a conversion factor we need one more conversion factor the miles to kilometers conversion factor which is given in the problem and of course the point of this problem is to convert kilometers to hours hopefully you can see that so you're just going to take kilometers try to get that out of there using your conversion factors and you see that you have one that has kilometers in it so using it you put the kilometers on the bottom miles on the top cancel out the kilometers we're left with miles if you don't want miles we want hours and we have a conversion factor that takes those miles and converts them to hours which is the rate so you put the miles on the bottom hours on the top cancel those miles out and then you just multiply across and the I don't know the tricky part I guess with this problem and some of these other problems is to remember the significant figures and in this one in particular there's two significant figures so we have to write out the number 5.0 and put your units hours okay so hopefully there are no problems with that one let me know if there are