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anonymous
 one year ago
A car journey of 380 km lasts 4 hours. Part of this is on a motorway at an average speed of 110kmh^1, the rest on country roads at an average speed of 70kmh^1.
(i) Write this information as pair of simultaneous equations.
(ii) Solve you equations to find how many kilometres of the journey is spent on each type of road.
So, I know what the answers are but I can't figure out how to get to it myself. Please will you help by showing me how?
anonymous
 one year ago
A car journey of 380 km lasts 4 hours. Part of this is on a motorway at an average speed of 110kmh^1, the rest on country roads at an average speed of 70kmh^1. (i) Write this information as pair of simultaneous equations. (ii) Solve you equations to find how many kilometres of the journey is spent on each type of road. So, I know what the answers are but I can't figure out how to get to it myself. Please will you help by showing me how?

This Question is Closed

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0use the relation v = d/t v= speed , d = distance travel on a motorway and t = time taken on the motorway so for motorway travel we have 110 = d/t and for the country roads 70 = (380  d) / (4  t)

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0so there are your 2 equations

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0writing the equation without fractions we get d = 110t 380  d = 70(4  t) to solve for t substitute d = 110t in the second equation 380  110t = 280  70t 380  280 = 110t  70t can you continue with this?

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0oh they want number of kilometers on each type of road I should have solved for d no matter when we find t we can then plug in the values to find the distances

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0fo you follow it OK so far?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yes, I am just a bit confused since those are not the answers my book got? I will give those too you now...

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0t(subscript 1) + t(subscript 2) =4; 110t(subscript 1) + 70t(subscript 2) = 380 Sorry I cant type the subscript numbers on my computer.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0That is what my textbook has said are the answers to the first question.

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0yes thats basically the same as i have bu they have called the two times t1 and t2 whereas ive called them t and 4  t because total time was 4 hours

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0if you solve for t you;ll find t = time for motoirway journey = 2.5 hours and so time foe road journey = 42.5 = 1.5 and distance for motorway = 110 * 2.5 = 275km and for raoad = 70 8 1.5 = 105 km

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0t1 + t1 = 4 110 t1 + 70 t2 = 380 is what your book has said

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0do you want me to show you how to solve this?

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0there is often a few different ways to solve problems like this.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Oh ok. I think I understand now thank you very much!

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0oh that should be t1 + t2 = 4

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0t1 being time for motorway and t2 time for roads

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Ok. You have helped me a lot!
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