need some help with a odds thing

[deviouz]

I read an old poker book about nl hold'em, and I found something interesting, the thing is, I have been trying to convert to nl for quite some time and this is new to me, I know how to calculate pot odds, but this I dont know how to calculate and is what I need help with, the situation the author writes about is this, you are in a satellite tourny trying to win a seat to the wsop, you are on the final table with only three other players remaining, the blinds has just gone up to 200/400, you have 1900 chips and are now required to use 400 to post the big blind, leaving you with 1500, your hand is KQ offsuit, the player on your immediate left opens with an allin bet of 1950, the other 2 players fold and it's up to you, you think the raiser has ace rag or an under pair, do you call or fold? the author explains why you should call, or why a call would be correct mathematically,
you are getting 2500 to 1500 in pot odds wich is 5 to 3 he writes,this means you need to win 37,5% to be making the right play mathematically since a KQ is 42% against ace rag and 38% against ace rag suited, and against an under pair you are close to even money, now to the part I need help with, he writes Im getting 2500 to 1500 in pot odds, that I understand, and he writes that it's 5 to 3, this I don't understand, I thought it was 1,67 to 1, I never seen 5 to 3? I have seen 5 to 1, 4 to 1, and even 3 to 1 but not to 3? how is this supposed to be calculated? and how does he calculate I need to win 37,5% to make in profitable?