Pankaj was travelling to point B from point A with speed of 45 km/hr. After 1 hour, Pratik also started to travel from point A to point B. Pratik reached the point B 30 minutes before Pankaj. If Pratik would have decreased his speed by 6 km/hr then both would have reached point B at the same time. Find the original speed of Pratik.
Answers
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Answer:
60
Step-by-step explanation:
Let the original time taken by Pankaj to reach point B from point A = x hours
Then, the original time taken by Pratik to reach point B from point A = (x−1.5) hours
Also
Let the original speed of Pratik = y km/h
As given, if Pratik would have decreased his speed by 6 km/hr then both would have reached point B at the same time.
Then,
y × (x − 1.5) = (y − 6) × (x−1)
⇒ y × (x − 1.5) = (y − 6) × (x−1)
yx − 1.5y = yx − 6x − y + 6
0.5y = 6x − 6
y = 12x − 12 ....(i)
So, 45 × x = y × (x − 1.5)
From equation (i), we get
45 × x = (12x−12) × (x−1.5)
⇒ 45x = 12x2 − 12x − 18x + 18
⇒ 12x2 − 75x + 18 = 0
⇒ 4x2 − 25x + 6 = 0
⇒ 4x2 − 24x − x + 6 = 0
⇒ 4x(x−6)−1(x−6) = 0
⇒ (4x−1)(x−6)=0
⇒ x = 1/4, 6
Since,
x = 14 is not possible.
So, x = 6
Therefore, the speed of Pratik = y
⇒ 12x − 12 = 60 km/hr