With a hammer and a knife.
A can opener.
To open cans.
How would you open cans without one
to open cans u crakhead!
They are used to open cans.
A regular can opener may struggle to open a number 10 can, which is larger and heavier than standard cans. Number 10 cans typically require a commercial or heavy-duty can opener designed for larger sizes. If using a regular can opener, ensure it is sturdy enough and has a wide enough cutting mechanism to handle the can’s thickness. If not, investing in a proper can opener for larger cans is advisable.
Please see http://www.answers.com/Q/What_is_a_can_opener
To open cans electrically, instead of using a manual crank.
"assuming we have a can opener", means: Knowing we have a can opener. Assuming means accepting without proof something is true or sure to happen. A can opener is a tool that can open cans and tins.
The can opener was invented before the microwave. The first can opener was patented in 1855, while the microwave oven was not invented until 1946. Can openers were developed to open sealed cans, which became popular in the early 19th century for preserving food, whereas microwaves were developed much later as a cooking appliance utilizing electromagnetic radiation.
The can opener. The tin can was invented in the late 17 hundreds but it was not until the middle 18 hundreds that people invented something to open them. Before this, the cans were made of very thick iron and impervious to almost any opener except a hammer and chisel.
In 1858, Ezra Warner patented his design for a can opener in America. Tin cans were first invented around 1810 but these cans were very thick and needed hammers and chisels to open. Later in the 19th century, cans became more thin like they are today. I got my information from Wikipedia.