Question

Find the total distance from Point A -> Point E, if the average distance is 56 km and the below data is given already:-
A ----- B -------- C -------------- D ---------- E
A -> B = 41 km, D -> E = 68

Answer 1

Answer:

When speed is constant distance will vary as time

Car A moves for 2 hours @ 25kmph ---------> d = s X t -------> 50 = 25 X 2

Car B moves for 3 hours @ 25kmph ---------> d = s X t --------> 75 = 25 X 3

Here (tA / tB) = (dA / dB) -----> time ratio = distance ratio = 2 : 3

2) Direct Proportionality between Speed and Distance (When Time is constant)

If time of two bodies or motion is constant, then distance will vary as speed

Here (S1 / S2) = (d1 / d2)

If two cars start simultaneously from opposite ends towards each other. They meet at point ‘C’

In this case distance covered by each car will vary as their speeds since they travelled for equal period.

Suppose the distance AB = 900 km Speed A = 25kmph Speed B = 20kmph

In this case their meeting point (C) will be (S1 / S2) = (d1 / d2) ------> 25/20 ----> 5/4 = 500 / 400 i.e. 500 kms from A

The

Example 2 :- A Man walked from his house to office at 5kmph and got 20 minutes late. if he had travelled at 7.5kmph, he would have reached 12 minutes early. The distance from his house to office is

Here s1 = 5kmph t1 = t2 + 20 + 12 s2 = 7.5kmph t2 = t2

(S1 / S2) = (t2 / t1) ------> (5/7.5) = (t2 / t2 + 32) ---------> 5t2 + 160 = 7.5t2 -------> t2 = 64 minutes

So distance = 7.5 X 1.7 (64 mins) = 8km