00:01
In this problem, let total work of emptying the tank be defined as simply w.
00:18
So, the rate at which the oil tanker works will be w by 4 work per hour and rate at which the auxiliary oil tanker works will be simply w by 9 work per hour.
00:45
Now, we are starting at 9 am, the work goes on till sometime and then it goes on again.
00:57
So, at this till from here to here, only oil tanker works and from somewhere here to here, both oil tanker plus the auxiliary oil tanker works.
01:17
So, this is 12 noon.
01:20
So, the work done here let that be w1.
01:24
Since the total work is w, so this one will be w minus w1.
01:29
So, time taken to complete w1 will be divided by the rate, rate only oil tanker is working.
01:44
So, it is w by 4.
01:46
This comes as 4 times w1 by w...