2 men at same time start walking towards each other from A and B 72 km apart. speed of A is 4 kmph . Spee

Question

2 men at same time start walking towards each other from A and B 72 km apart. speed of A is 4 kmph . Speed of B is 2 kmph in 1st hr,2.5 in 2nd, 3 in rd hr and so on…when will they meet at one single point between A and B .?

plz try to explain in detail

thanks

Answer 1

For this question, we need to know that distance = velocity x time.  The total distance travelled needs to be 72 km.

Lets represent the total amount of time during the journey as t (hours).  Knowing this, person A will have travelled 4t km during the trip.

We can setup up an equation for distance using what we know.  We don't know how long it will take, but we can guess that it will take somewhere betweem 8-9 hours (as 72/2 =36 and 36/4 is 9).  It is just a guess to start from.

4t + 2(1hr) + 2.5(1hr) + 3(1 hr) + 3.5(1hr) + 4(1hr) + 4.5(1hr) + 5(1hr) +5.5(1hr)+6(t-8 hrs) = 72 km

Note that the first term corresponds to person A's distance and all subsequent terms correspond to person B's distance.  Person B's distance is broken up by hour.

Solving, this works out to be:

10t + 30 - 48 = 72

t = 9 hrs

Since this corresponds to the interval we guessed, it is the correct answer.  However if you chose a different interval, you can use this as an iterative process until you get it to work.  I.e. if you chose the interval 5-6 hours, you would have got a time value where t > 6 hours, so you know that it actually took longer.  Similarily, if you chose 10-11 hours you would have got a value of t < 10, so you would know that it actually takes less time.

Answer 2

Why dont you ask your teacher personally to explain this type of questions instead of asking on yahoo answers.