Question

if instead of going at my usual speed of 30kmph, i go to office ar 40kmph, i reach office 10 minutes early. what is the usual time i take to reach office and what is the distance i travel?

Answer 1

Answer : Let time taken to reach office at normal speed of 30 mph = t hours

Let distance from my home to office = d miles

we know ,

Speed = distance /time

therefore , 30mph = d /t

or t = d/30 -----Equation (1)

Therefore time taken to reach office when I go with speed of 40kms/hr = t2 hours.

Speed = Distance /time

40 mph = d /t2

or t2 = d/40----- Equation 2 .

From the problem description ,

t1 - t2= 10 minutes

Equating t1 and t2 from equation 1 and Equation 2 , we get

d/30 - d/40 = 10 minutes

d ( 1/30 - 1/40) = 10/60 hours (Converting minutes into hours )

d (40 - 30 )/40*30 = 10/60

d(10)/1200 = 10/60

or d = 10/60*1200/10

or d =20 miles .-----Equation 3

From equation 1 and 3 , we get

t1= 20 /30 = 2/3 hours

t1= 2/3*60 minutes

t1= 40 minutes

Hence , Usual time taken by you to reach office is 40 minutes .

And distance travelled by you to reach office is 20 miles.

Hope this helps you.

Thank you :)

Tawseef ^-^