Answer by yuuki for Typo in math brainteaser book?
The book formula is horribly wrong, mistakes were made.No need for arbitrary, just use $1$ or $x$Speed upstream: $x/20=v-curr$Speed downstream:...
View ArticleAnswer by Carl Christian for Typo in math brainteaser book?
The problem can be phrased as a nonsingular system consisting of 2 equations with 2 unknowns. Let $d$ denote the distance between the two piers, let $v$ denote the speed of the ferry in the absence of...
View ArticleAnswer by gnasher729 for Typo in math brainteaser book?
Let the distance between the piers be d, and the distance the current takes you in an hour c.So in 20 hours you cover d + 20c going upstream. In 15 hours you cover d - 15c going downstream. In 60 hours...
View ArticleAnswer by DJohnM for Typo in math brainteaser book?
EDIT: all this was said faster and better in @Erics solutionThe original question makes no mention of any distance unit. So you can't determine the distance. Just go through the printed solution to the...
View ArticleAnswer by Eric for Typo in math brainteaser book?
The book is making a mistake. That entire second half is nonsense, and the formula is incorrect.In particular, it’s impossible to determine the speed of the river since there is no unit of distance in...
View ArticleAnswer by ryang for Typo in math brainteaser book?
Equating the distance between the two piers:$$(b-r)20=(b+r)15\\b=7r.$$So, on still water, the one-way journey time (distance/speed) is $$\frac{(b+r)15}{b}\text{ hrs}=\frac{120}7\text{ hrs}.$$Addendumit...
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Typo in math brainteaser book?
A steamboat leaving pier $1$ takes $20$ hours to go against the current upriver to pier $2$. It can return downriver with the current from pier $2$ to pier $1$ in $15$ hours. If there were no current,...
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