Let’s assume the length of each train is ‘L’ and the speeds of the two trains are ‘V₁’ and ‘V₂’ respectively.
When the trains are moving in the opposite direction, their relative speed is the sum of their individual speeds. The total distance they need to cover is the sum of their lengths. Since they cross each other completely in 5 seconds, we can set up the following equation:
(V₁ + V₂) × 5 = 2L
When the trains are moving in the same direction, their relative speed is the difference between their individual speeds. The total distance they need to cover is the difference between their lengths. Since they cross each other completely in 15 seconds, we can set up the following equation:
(V₁ – V₂) × 15 = 2L
Now, let’s solve these equations to find the ratio of their speeds.
From the first equation, we have:
(V₁ + V₂) × 5 = 2L
V₁ + V₂ = (2L) / 5
From the second equation, we have:
(V₁ – V₂) × 15 = 2L
V₁ – V₂ = (2L) / 15
Let’s add these two equations together:
V₁ + V₂ + V₁ – V₂ = (2L) / 5 + (2L) / 15
2V₁ = (6L + 2L) / 15
2V₁ = (8L) / 15
V₁ = (4L) / 15
So, the speed of the first train is (4L) / 15.
Now, let’s substitute this value back into the first equation to find V₂:
(4L) / 15 + V₂ = (2L) / 5
V₂ = (2L) / 5 – (4L) / 15
V₂ = (6L – 4L) / 15
V₂ = (2L) / 15
Therefore, the speed of the second train is (2L) / 15.
The ratio of their speeds is given by:
(V₁ / V₂) = ((4L) / 15) / ((2L) / 15)
(V₁ / V₂) = 4L / 2L
(V₁ / V₂) = 2
So, the ratio of their speeds is 2:1.
saying 20%alcohol in 15 litre solution.
It means (20/100)*15=3 litres
Now 5 litre of water is added not alcohol.
So it means only the volume of solution is increases by 5 not alcohol.
It means 15+5=20
Now % of alcohol is
(3/20)*100=15%.
1261
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P Q R S
TP -> UQ -> RV -> SW
Answers-
U sits opposite to S
Q sits in between S and R (after interchange)
A is travelling at 50kmph, B is travelling at 40
kmph……..according to the formula
time taken to meet = distance between them
———————-
relative speed of two vehicles
so, time taken to meet= 15/(50-40)=15/10=3/2hrs
Ravi do a work in 30 days
Prakash do a work in 40days
then both work together 1/30+1/40=70/1200
then solve values 120/7 is 17(1/7) days
Friday
The phrase is usually ‘like looking for a needle in a haystack’. It describes a task that is virtually impossible because you would have to search a huge area
it was a friday.
Let d = 7r. And use distance is = rate × time
7r= ( r+12) 5
7r= 5r + 60
Subtract 5r from both sides
2r = 60
Divide out 2
Rate = 30 km/h
Original question 30 km/h × 7 = 210
30 +12 = 42× 5 = 210
C will take 4 days and the total number of days taken by a,b and c will be 12 days.
2 and half day.