Question

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Rajesh can walk at 5m/s or cycle at 20m/s. He takes 45s to cover a distance of 600m using a combination of the two modes of transport. How long did Rajesh cycle?


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Answer 1

Answer:

20 seconds

Step-by-step explanation:

Given:

Speed he has of walking = 5 m/s

Speed she has on cycle = 20 m/s

Formula used:

Distance = Speed × Time

Calculation:

Let time taken on walking be p

Let time taken on cycle be q

According to the question:

5p + 20q = 600 ----(1)

(p + q) = 45 (Total time)

⇒ p = (45 – q) ----(2)

Now,

Putting the value of p in equation (1), we get

⇒ 5(45 – q) + 20q = 600

⇒ 225 – 5q + 20q = 600

⇒ 15q = 600 – 225

⇒ 15q = 375

⇒ q = 375/15 = 25

Again, Putting the value of q in equation (2), we get

⇒ p = (45 – 25) =20

∴ Rajesh cycle covered by time 20 seconds.

By allegation method

Speed = Distance /Time = 600/45 ⇒ (40/3) m/s

Speed of walking

The ratio of walking to cycle speed = 20 : 25

Speed is inversely proportional to time

The ratio of walking to cycle time = 25 : 20

Total time = 45s

25x + 20x = 45

x = 1 sec

∴ The time taken to cycle is 20 × 1 = 20 sec

Hope it's helpful