Question

Ramu travels at the speed of 40 km/hr. He reduces his speed every hour by 4 km. How much time would he take
to travel 216 km?​

Answer 1

Answer:

I am solving it please wait

Answer 2

Answer:

Step-by-step explanation:

Just a simplifying assumption. The bus increases speed every 60 minutes by 3kmph in a step fashion.

If it were 21 kmph straight, it would have taken 12 hrs. We are looking for a sum: 21*1+24*1+27*1… =252;

The problem translates to an Arithmatic Progression series sum of ‘n’ terms with 21 as the first term, 3 as the common difference; we find n by solving

(21+21+(n-1)*3)*n/2=252;

39n+3n^2–504=0;

n^2+13n-168=0;(n-8)(n+21)=0:

n=8 being the plausible answer.

Another way:

We are looking at an area under a stair case graph, base height 21, height increases by 3 Y units at every 1 X unit;

Might as well replace the stair case by a triangle, area remaining unchanged,

21*x+1/2(x)(3x)=252;

x^2+14x-168=0; (x-8)(x+22)=0;

x=8 is the plausible solution.

Answer 8hrs.

I HOPE IT HELPS you and you can use this METHOD also