How many stundents passed in class 2 in year 2000, we don't have data for that right ?? Shouldn't the question say, how many studeents passed to class 2 in the year 2000 ?
Yes! you're correct. But here, we are assuming that the joining year of students is in the year 1999, and they will pass the exam in the year 2000 ( after one year if they don't fail in that class).
I am unable to understand the question related to the mobile and tablet manufacturing. It is stated that all the mobiles and tablets manufactured are sold completely. And then it says that after 2 years mobiles manufactured and not sold are discarded as so on. Also why are we taking 25% and 10% of the 2009 units directly for calculating units to be discarded after 4 years. Shouldn't it be the percentage of the remaining mobiles/ tablets discarded. For eg: In case of Q3- Tablets discarded after 4 years is 20% of (20-2).
Now, the user who bought that phone will discard it either after 2 years or 4 years or 6 years.
In the question, it is given that 2 years after manufacture, 25% of the mobiles and 10% of the tablets manufactured are discarded. 4 years after manufacture, another 25% of the mobiles and 20% of the "tablets manufactured" are discarded. We take the percentage of manufactured devices; therefore, we can't take the percentage of remaining devices.
