The metric system is easy to use because it is based on units of ten. how many centimeters are there in 100 meters?

The answer is:  " 10,000 cm " .

Note:  100 cm = 1 m  (exact measurement); in which: 

                     "cm" = centimeter(s) ;
                      "m"  = meter(s) ;

  100 m = ? cm ?

100 m * (100 cm / 1 m)  =  __?__   cm  ;

The units of "m" cancel out;  and we have:

(100)* (100 cm) = 10,000 cm .

The sum is 2,160, no problem