Question

1. The cost of fuel for running a train is proportional to the speed generated in km/h. It
costs 40 per hour when train is moving with 20 km/h. What would be the cost of fuel
per hour, if the train is moving with 60 km/h?​

Answer 1

Answer:

₹120

Step-by-step explanation:

₹40 = 20kmph

₹x = 60kmph

cross multiply

20x = 40*60

x = 40*60/20

x = ₹120

Answer 2

It costs Rs 120 per hour if the train is moving with 60 km/h

Solution:

Given that,

The cost of fuel for running a train is proportional to the speed generated in km/h

Therefore,

$\text{cost of fuel } \propto \text{ speed in km/hr}$

Let "x" be the cost of fuel

Then, "y" be the speed in km/hr

Then we get,

$x \propto y$

x = ky ------- eqn 1

Where, k is the constant of propotionality

It  costs 40 per hour when train is moving with 20 km/h

Therefore,

x = 40 and y = 20

Substitute in eqn 1

40 = k(20)

k = 2

What would be the cost of fuel  per hour, if the train is moving with 60 km/h?​

x = ?

y = 60

k = 2

Substitute in eqn 2

x = 2(60)

x = 120

Thus it costs Rs 120 per hour if the train is moving with 60 km/h

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