In 90 kgs of potatoes there are 0.09 tons, to achieve this take 90 and just divide by 1000.

To convert 400 kgs into tons divide by 1000 giving 0.4 tons.

You have 200 kgs of barley but you need to know how many tons that is. To get the answer divide by 1000 which gives you 0.2 tons.

How many tons of wheat are there in 620 kgs? Just divide by 1000 to get the answer of 0.62 tons.