Train A takes 45 minutes more than train B to travel a distance of 450 km. Due to engine trouble speed of train B falls by a quarter, so it takes 30 minutes more than Train A to complete the same journey. What is the speed of Train A (in km/hr)?

Question

নিচের অপশন গুলা দেখুন

• 90
• 120
• 100
• 110

Answer 1

সঠিক উত্তর হচ্ছে: 100

ব্যাখ্যা: Let speed of A = A km/hr and speed of B = B km/hr
According to the question;
⇒ 450/A – 450/B = 45/60
⇒ (1/A – 1/B) = 1/600 ---- (1)
And
⇒ 450/(3B/4) – 450/A = 30/60
⇒ 4/3B – 1/A = 1/900 ---- (2)
Adding both the equations;
⇒ 4/3B – 1/B = 1/600 + 1/900
⇒ 1/3B = 5/1800
⇒ B = 120 km/hr
Putting this value in equation 1;
⇒ 1/A = 1/600 + 1/120 = 6/600
⇒ A = 100 km/hr
∴ Speed of A = 100 km/hr