A boat travels 40 m upstream in 3 hours, going downstream it can travel 42 miles in the same amount of time what is the speed of the current mph
in Pre-Algebra Answers by

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
To avoid this verification in future, please log in or register.

1 Answer

Let b=speed of boat and c= speed of current. Time to go upstream against the current is 40/(b-c). Time to go downstream with the current is 42/(b+c). So 40/(b-c)=42/(b+c)=3. Take the first pair of expressions: 40(b+c)=42(b-c) (cross-multiplying); 40b+40c=42b-42c; 82c=2b, making b=41c mph.

Also, 40/(b-c)=3, 40=3b-3c=123c-3c=120c, making c=40/120=1/3 mph.

Check that this is satisfied in 42/(b+c)=3: 42=3b+3c=123c+3c=126c, making c=42/126=1/3 mph.

 

 

by Top Rated User (775k points)

Related questions

Welcome to MathHomeworkAnswers.org, where students, teachers and math enthusiasts can ask and answer any math question. Get help and answers to any math problem including algebra, trigonometry, geometry, calculus, trigonometry, fractions, solving expression, simplifying expressions and more. Get answers to math questions. Help is always 100% free!
85,248 questions
90,479 answers
2,127 comments
80,090 users