Error in Ciaffone's Omaha Book?

In his "Omaha Holdem Poker" book, Bob wrote that with two cards to come, a twenty-way straight draw will make a straight over 70% of the time. Curious about how much over 70% a 20-outer would hit, I tried calculating the probability myself. I approached the problem by first calculating the probability of missing on both the turn and the river.


p(miss on turn) = (45-20)/45

p(miss on river) = (44-20)/44

p(miss turn & river) = (45-20)/45 * (44-20)/44 = .3030


Therefore, p(hitting) = 1 - .3030 = 69.7%


I'm pretty sure I did this right, but would appreciate confirmation. My math skills are a bit rusty.

Your math looks fine to me. So there's a minor error in the book. If the percentage had been, say, 72% rather than 69.7%, would this change the way you play this hand?

This error in isolation is of no consequence to one's play. However, a careless error like this raises the question of whether a book may contain other, potentially more costly factual errors. Having now read most of the book, I do not think it has this particular problem.