Walking (6/7)th of his usual speed, a man is 12 minutes too late.
The usual time taken by him to cover that distance is:

• Let us consider the usual speed=x meters/second,time=t seconds and distance=d meters.If the speed is equal to x,the man reaches the distance d in t seconds.
  Therefore x=(d/t).
  
  Now if the man travels with (6/7)th of his usual speed,the man is 12 minutes late i.e., when speed=(6/7)x meters/second,time=[t+(12*60)]seconds.
  Therefore (6/7)x=d/(t+720),but x=(d/t)
  therefore (6d/7t)=d/(t+720),solving this we get 6(t+720)=7t which implies t=720*6=4320 seconds i.e., t=72 minutes.
• 9 years agoHelpfull: Yes(1) No(0)
• 6/7th of usual speed means time taken will be 7/6th of usual time...
  Therefore New time= 7/6th of usual time...
  New time- usual time= 7/6-1
  =1/6
  So 6*12=72mins
• 9 years agoHelpfull: Yes(1) No(0)
• x-6x/7=12
  x=12*7
  x=84min
  
• 9 years agoHelpfull: Yes(0) No(1)
• if x= original speed & y=original time
  then
  x------>y
  6x/7------>y+12
  so difference in speed=x/7 is equivalent to 12 min
  thus, x=12*7=84
  since distance remains same in this both cases,
  xy=6x/7(y+12)
  x=84
  so, y=72(reqd time)
• 9 years agoHelpfull: Yes(0) No(0)