Subject: Why does folding paper make it stronger?

Am doing an experiment with children to test the strength of a variety of 
paper (newspaper, tissue paper etc) by attaching weights to the end of a strip 
of paper via a hook until it tears. Am asking the children to think of how we 
can strengthen the paper to hold more weight. Obviously folding the strip will 
make it stronger and thus hold more weight. But whats the scientific 
explanation to give a 6 year old!? Many thanks

Re: Why does folding paper make it stronger?