1. (Difference
between speeds/Maximum Speed)
= (54kmph-45kmph)/ (54kmph) = (9/54) hrs
= (9/54)*60mins= 10 minutes
2. Distance = speed * time
Given distance = (100+400)
meters
Speed=90kmph= (90*5/18) =25mps
500 = 25 * time
Time= 500/25 = 20 sec
3. (2*a*b)/ (a-b) since same direction
= (2*9*6)/ (9-6) = 108/3 =36 seconds
4. Train A starts at 9AM
and travels at 60kmph
In 2hrs i.e. by 11AM it
travels 120kms
Then train B starts with
100kmph
Time to
meet=distance/relative speed
=120/ (100-60) = 120/40 =
3hrs
So 11AM+3hrs = 2PM
5. (2*a*b)/ (a+b) since opposite direction
= (2*10*15)/ (15+10)
= 300/25 =12 seconds
6. A travels for 3hrs at
80kmph =240km
B travels at 110kmph
Time to
meet=distance/relative speed
=240/ (110-80) = 240/30
= 8hrs
So distance =8*110km =
880km
7. (Product of 2 speeds / difference of speeds)*time in
hours
=
(30*40/40-30)*(15/60)
= (1200*15/600) = 30kms
8. Distance= (total time * product of
speeds)/ sum of speeds
= (5*3*2)/ (3+2) =6km
So the distance between
school and village is 12/2=6kms
9. (Product of 2 speeds / difference of speeds)*time in
hours
= (10*12/2)(10/60)
= (120*10/120) = 10kms
10. Distance = (2*(time)*speed1 * speed2)/
(speed1+speed2)
Distance= (2*10*21*24)/ (21+24)
Distance=224km
11. Distance= 120 km
Sum of speeds = (18+12) = 30kmph
Therefore time =distance/speed
=120/30 =4hrs
So the dogs travels 25*4=100km
12. Distance=200meters
Speed=72kmph= (72*5/18)
=20 mps
Time= distance/speed =200/20=10sec
13. Speed ratio for car: bus= 3:4
So Time ratio car: bus = 4:3
Given time of car
is 24minutes =>4*x= 24 so x=6
So time for bus =3*x =3*6 =18minutes
14. P travels for 4hrs at 40kmps speed so 160km of
distance is covered
Given total distance = 340 so 340-160=180kms
To travel 180kms the time taken = distance/sum of speeds
=180/ (40+50)= 2hrs
So 10AM + 2hrs =12PM
15. Extra travelled distance*(sum of speeds/difference of
speeds)
= (180*175/15)
=2100km
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