priyaranjan

• Mar 12th, 2006

 

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

=12.8km/hr

on return journey he travels 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

sunny jain

• Mar 14th, 2006

 

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 proportional to distance.that's 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..........?

vikraman

• Jun 24th, 2007

 

Let average speed uphill be x km per minute & downhill be y km per minute

Covert every thing to minutes

The required equation is 8/x+24/y=150 and 24/x+8/y=290

Solve equation y=.463 km per min

x=.088 km per min

Gives downhill speed=24.36 kmph

Uphill speed=5.28 kmph

If you want to check the answer substitute in the first two equations