Question 945122
Half of the journey is 4 km. At a rate of 6 km/hr, it takes (4 km)/(6 km/hr)=2/3 hr to walk the first half. Since she must finish in 1 hour, she has 20 minutes (1/3 hr) remaining to walk the second 4 km so 4km/(1/3 hr)=12 km/hr
ANSWER Susan must walk the second half at 12 km/hr to average 8 km/hr