he travels 8+24 32 kms in 2hrs30mins so avg speed during that time 32/2.5

12.8km/hr

on return journey he travells same 32 km in 4 hrs 50 mins

so speed during this time 32/4.83 6.62km/hr.

therefore avg speed during complete journey 2*x*y/(X+y) 12.8*6.62*2/(19.42) 8.78

well the question is asking bout av speed during uphill nad downhill so i m tell u the way to get uphill similarly u can get downhill speed........

let asume that cyclist go with gthe same speed during uphill and downhill as he go with same speed so time will proportinal to distance.thats is 1: 3. so in fst case time will be 1/4(2.5) 5/8. in secnd case it will be equal to 1/4(4 5/6) 29/24. so adding the time total time in uphill will be 44/24. so av. speed will be 16/(44/24) 96/11..........