little bit of maths into our boring lives

[bloody-orc]

A tractor works 6h on a field. other tractor sees it and comes to help. together thew work for 4h and then the task is done. how many hours will it take for each of those tractors to do the task on theyr own (from the beginning to the end) if second tractor will do the task 3hours faster than the first tractor.

what do you get for the answer. plz give the way you got the answer aswell.

 

[Someone Electro]

1st tractor dose it in 3,5h
2nd tractor dose it in 6,5h

 

[Someone Electro]

No wait thats not right!!!

Hmmm...

I dont think its posible becose you cant figure out how fast the 1st tractor is to figure out how much fater those 3 h are.

 

[Optikon]

Tractor A (slow one) can do it by himself in 22 Hours.
Tractor B (3 times faster) by himself would take 7 hours 20 minutes.

:lol: :lol: :lol:

Sounds like my yard! So whats the answer?

 

[bloody-orc]

MartinM57 sed:

Say tractor A takes A hours to do the field
Say tractor B takes B hours to do the field

In 1 hour, tractor A does 1/A of the field
In 1 hour, tractor B does 1/B of the field

The field was done by 10 hours-worth of tractor A and 4 hours-worth of tractor B

So ...
10/A of the whole hours to do the field by tractor A +
4/B of the whole hours to do the field by tractor B =
the whole hours to do the field

If the whole hours to do the field = X, then

(10/A * X) + (4/B * X) = X

Divide throughought by X

10/A + 4/B = 1

...but B = A - 3

So
10/A + 4/(A-3) = 1

which can be solved for A (via a quadratic equation - I'll leave you to do that!)

...and B = A-3, leading to B


Do I get the Christmas mince pie?

 

[Optikon]

Tractor A (slow one) can do it by himself in 22 Hours.
Tractor B (3 times faster) by himself would take 7 hours 20 minutes.

:lol: :lol: :lol:

Sounds like my yard! So whats the answer?

Edit: I mis-read and did for Tractor B being 3 times faster than A not 3 hours less. Fixing this leads to 8.21 Hours & 5.21 hours same analysis as Martin. His description is poor however.

 

[panic mode]

Optikon,

how is that? slow tractor can do it in 8 hrs alone and fast tractor in just 5hr when they both have been in field for 10hrs working together?
what if slow tractor can do it in 15 hours and fast in 12?

 

[mstechca]

A tractor works 6h on a field. other tractor sees it and comes to help. together thew work for 4h and then the task is done. how many hours will it take for each of those tractors to do the task on theyr own (from the beginning to the end) if second tractor will do the task 3hours faster than the first tractor.

what do you get for the answer. plz give the way you got the answer aswell.

Lets see...

4/6 = 2/3
2/3 = 6/9

So wouldn't it be 6 hours for the fast tractor and 9 hours for the slow one?
or is there something I am missing?

 

[bloody-orc]

correct answer is 15h and 12 h like panic mode sed.

 

[Optikon]

Optikon,

how is that? slow tractor can do it in 8 hrs alone and fast tractor in just 5hr when they both have been in field for 10hrs working together?
what if slow tractor can do it in 15 hours and fast in 12?

yeah, the point was that it was incorrect (Martins method)!

 

[mstechca]

I am so lost

 

[bloody-orc]

the answer cant be less than 10 h for rhe slow tractor so all the answers you have told are incorrect. martins is correct: it gives 15 and 12.

 

[panic mode]

hehehe

 

[mstechca]

the answer cant be less than 10 h for rhe slow tractor so all the answers you have told are incorrect. martins is correct: it gives 15 and 12.

wait a sec....

A tractor works 6h on a field. other tractor sees it and comes to help. together they work for 4h and then the task is done.

It specifically says one tractor works 6 hours on a field. and both 4h.
This could mean both tractors work 4 hours, and one tractor leaves and the other one takes 2 more hours to finish!

your question didn't state that one tractor works 6h, and the other tractor comes to help and they work for 4 MORE hours!

Quite deceiving.

No wonder I'm lost!

 

[bloody-orc]

1 works alone for 6 h,s 2'nd comes to help and they work more 4h together

 

[Someone Electro]

I figured that triangle thing out long ago.

The angle is tweaked a bit.Try to draw an stait line along the triangle.And you will see that its aculy an 4 edge shape.One edge is very close to 180°.

 

[akg]

in the second the hypotenuse side is not same as the first one..there is a change in partial area covered .