A quick help needed

[alisan]

A train travelled a distance of 20km from town A to town B at a speed of xkm/h. If its speed is decreased by 1km/h, the time taken is one hour less. Find the initial speed of the train.

 

[Ishuda]

A train travelled a distance of 20km from town A to town B at a speed of xkm/h. If its speed is decreased by 1km/h, the time taken is one hour less. Find the initial speed of the train.

First of all, read the problem:
speed decreased then time taken is less
Generally the fastest traveler covers the same distance is less time, so that doesn't make sense to me. So re-read the problem. Yep that's what it says, so it looks like what we really have to prove is that there is no answer 'in the Real world'.

Two thing to do. First the most difficult for a lot of people, turning the word problem into equations. To help in this there are pages which offer hints and practice about how to do this, see
http://capilanoelementary.weebly.com/uploads/8/0/7/7/8077152/key_words_for_math_word_problems.pdf
for example or search on something like
math word problems key words and catchy phrases

First define the variables you will need. This has partially been done here for you by making x the speed of the train. But it also looks like we will need two times so call them time1 for the x speed and time2 for the decreased speed

Now some formulas. We are given time so how is speed related to time?
distance = speed * time
or, rearranging,
time = distance / speed
So, for the train traveling at speed x for 20 km we have
time1 = distance / speed = 20 / x
and for the train traveling at a speed 1 km/hr less we have
time2 = distance/ speed = 20 / (x-1)

We are told that time2 is one less than time1. Can you take it from there?

 

[Steven G]

Assuming speed is INCREASED:

A(@x).............20...............>(k hours)B : k = 20/x [1]

A(@x+1).........20...............>(k-1 hrs)B : k-1 = 20/(x+1) [2]

[1] and [2]: 20/x = 20/(x+1) + 1
Solve for x

There you go assuming again. You'll never learn will you.

 

[alisan]

Thank You All, Thank you ISHUDA, I worked it out inform of Quadratic equation.Denis: thanks too for your contribution.Am glad.