The following utility will enable you to convert mass/weight expressed in pounds to tonnes
To convert pounds to tonnes divide by 2204.622
How many tonnes of butter are there in 580 pounds? Just divide by 2204.622 to get the answer of 0.26308365 tonnes.
You have 900 pounds of sugar but you need to know how many tonnes that is. To get the answer divide by 2204.622 which gives you 0.40823325 tonnes.
To convert 340 pounds into tonnes divide by 2204.622 giving 0.15422145 tonnes.
In 20 pounds of lentils there are 0.00907185 tonnes, to achieve this take 20 and just divide by 2204.622.
You've got 950 pounds of salt but someone only wants to buy that in units of tonnes, to change the units divide by 2204.622. Now you have 0.43091287 tonnes.