Question 322911
let the house distance be x km

time = distance /rate

daily  time taken = x/100
on this day time taken = x/80 
The difference in time = 1 hour
..
x/80-x/100=1
100x-80x / 8000 =1
20x/8000=1
multiply by 8000 on both sides
20x= 8000
x=400 km