Josiah ran 4/5 mile. how many tenths are equal to 4/5 mile. using a bar duagram

Multiply both numerator and denominator by 2.
4*2 = 8 & 5*2 = 10
4/5 is thus equal to 8/10 or eight-tenths. 

With a bar duagram, just divide/split it up evenly into 5 parts then colour in 4 of the pieces. Then, divide as a whole now make it so there's 10 parts - do this by splitting each 5 parts into 2 (put line through middle) to make 10 parts. Now you will see that there is 8 parts that are coloured in for 10 pieces compared to 4 coloured parts when there was 5 pieces.