the last digit is the last digit of 1!+2!+3!+4!+5!+6!+7!+8!+9! because all the others end in zero, zero, zero! (Reason: for example, 36! 36x35x34x33x32x31.......x10x9x8.....3x2x1) I honestly dont know the second it could be anything from 0 to 9. Im soory this awnser is probably not helpful.
Figure out how far you walk in one minut at 3 miles per hour and figure out how far you walk in a minute at 4 miles per hour and add the 3 miles to itself and the 4 miles to itself and then add how far you go in 1 minute for the three or the four to the three or the four total and repeat until you either pass your friend or catch up to her and if you pass her figure out how far you are from her and subtract that from where you are
I am sorry if this is not helpful. I try my best =>