Question 984629
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D=distance; R=original rate; T=original time
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Originally:
D=RT=R(6hrs)=6R hrs
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After speed increase:
D=(R+24kph)(6hrs-1hr)=(R+24kph)(5hrs)=5R hrs+120k
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Since distance to office is the same:
6R hrs=5R hrs +120k
R hrs=120k
R=120k/hr
His original speed was 120 kph.
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(6hrs)(120kph)=720 km
The distance to his office was 720 kilometers.
. 
CHECK:
720km=(R+24kph)(6hrs-1hr)
720km=120kph+24kph)(5 hrs)
720km=(144kph)(5hrs)
720km=720km