Multiple business under one pvt ltd or multiple pvt

Hi 

was wondering, if we wanted to do multiple business activities, do we need to have multiple pvt ltd, 

or one pvt ltd is suffice to do multiple business 

say while registration of pvt, we have given nature of business as 

1. Trading electronics, Garments, manufacturing chemicals, 

later after few months wanted to add business like

2. Events management, Educational consultants, Shoes manufacturing. Real estate constructions 

can we do it ? if yes is it easy and costly? or we are not supposed to do all types of business in 1 pvt ltd. what is the rule?

Or do you suggest, its better to sit down and List all the business activities, we do in future and Add them during first time Registration of Pvt ltd?  

whats the general advise