Morgan needs a board that is 80/100 meters long. javier hands him a board that is 0.8 meter. can morgan use that board?

 "Yes." 

Explanation:

" Yes;  since:  "80/100" m  =  "8/10" m  =  "0.8" m  .

Note:  Cancel out a "zero" from BOTH the "80" (in the numerator) and the "100" (in the denominator); to get:  "80/100" = "8/10" .

This is the same as:  "80/100" = "(80÷10) / (100 ÷10)" = "8/10".

Note that:  "8/10" can be written as the decimal equivalent:  "0.8" .

As such:   "80/100"  m  =  "8/10"  m =  "0.8" m  .