DARE TO SOLVE -DAY 2
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DARE TO SOLVE -DAY 2
1.Progressive Express left for New Delhi,Increasing its Speed in each hour.It Started its Journey from Lucknow,but after four hours of its journey it met with accident.Its Speed in the Fourth hour was 7/5 times that of the third hour and the speed in the third hour was 10/7 times that of the second hour and in the second hour it was 7/5 times that of the first hour.If it would have been travelled with the half of the speed that of the third hour,then it would have gone 160 km less in the same time(i.e., in four hours).The average speed of the train during the journey of 4 hours was:
Solution:
Let the Speed of the 1st hour is X km/hr
Speed of 1st Hour | Speed of the 2nd hour | Speed of the 3rd
hour |
Speed of the 4th hour |
X km/hr | (7/5)X km/hr | (10/7) *(7/5)X=2Xkm/hr | 2X * (7/5)=(14/5)Xkm/hr |
Therefore,The Distance Travelled in 4 hours
=X+(7/5)X+2X+(14/5)X
Total Distance = km
Average Speed=Total Distance/Total time
= (36/5)X ÷ 4
=(9/5)X km/hr
The train travelled during the journey of 4 hours,at the rate of Xkm/hr which is half of the third hour’s Speed is 4X km
=(36/5)X – 4X =160km
= X=50
Average Speed of the Journey for 4 Hours= 9/5 X
= 9/5 * 50
=90 km/hr
2 comments
Avg speed OK… 9/5x.. Correct.. Then how 160 km. Any one explain
It is given in the Question,
That if in the third hour it travelled half of the speed then it would cover 160 km less.So only we had written 160 km.