From point A to B, there is only uphill and downhill with no ground level. Mr Lim drives uphill at a speed of 20 km/h and downhill at a speed of 35 km/h. If he takes 4.5 hours to drive from point A to B and 3¾ hours from point B back to point A, what is the distance between the two points?

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

u=uphill distance, d=downhill distance. AB=u+d when going from A to B, and BA=d+u when returning, because downhill←→uphill when Mr Lim changes direction.

Distance=speed×time.

Time=distance/speed, 9/2=u/20+d/35; 15/4=d/20+u/35.

Multiply through by 140:

(1) 630=7u+4d; (2) 525=7d+4u.

4×(2) is 2100=28d+16u and 7×(1) is 4410=49u+28d=49u+2100-16u=2100+33u.

4410-2100=2310=33u, u=2310/33=210/3=70km.

So 4d=630-490=140, d=35km. AB=70+35=105km.

 

 

by Top Rated User (776k points)

Related questions

1 answer
asked Jun 11 in Trigonometry Answers by okdoyn Level 1 User (360 points) | 39 views
1 answer
asked Jun 10 in Algebra 1 Answers by okdoyn Level 1 User (360 points) | 48 views
2 answers
asked Jun 9 in Trigonometry Answers by okdoyn Level 1 User (360 points) | 51 views
1 answer
asked Jun 9 in Trigonometry Answers by okdoyn Level 1 User (360 points) | 39 views
1 answer
asked Jun 9 in Algebra 1 Answers by okdoyn Level 1 User (360 points) | 41 views
1 answer
asked Jun 9 in Algebra 1 Answers by okdoyn Level 1 User (360 points) | 34 views
1 answer
asked Jan 28 by anonymous | 111 views
1 answer
asked Nov 25, 2019 by anonymous | 83 views
1 answer
asked Nov 25, 2019 by anonymous | 66 views
1 answer
asked Nov 25, 2019 by anonymous | 52 views
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!
85,270 questions
90,544 answers
2,153 comments
84,499 users