Question

plzz ans my question I will mark it as best​

Answer 1

Answer:

42 km/hr

Step-by-step explanation:

(i)

Given, Distance = 63 km.

Let the original average speed be 'x' km/hr.

Time = Distance/Speed = (63/x) hours.

(ii)

Given,Distance = 72 km.

Given, Speed = (x + 6) km/hr.

Time = Distance/Speed = (72/x + 6) hours.

Now,

Given that it takes 3 hours to complete the journey.

⇒ (63/x) + (72/x + 6) = 3

⇒ (63x + 72x + 378)/x² + 6x = 3

⇒ 63x + 72x + 378 = 3(x² + 6x)

⇒ 135x + 378 = 3x² + 18x

⇒ 3x² - 117x - 378 = 0

⇒ x² - 39x - 126 = 0

⇒ x² - 42x + 3x - 126 = 0

⇒ x(x - 42) + 3(x - 42) = 0

⇒ (x - 42)(x + 3) = 0

⇒ x = 42, -3{As speed cannot be negative, so x ≠ -3}

⇒ x = 42.

Therefore, average speed of the train is 42 km/hr.

Hope it helps!

Answer 2

Let x and (x + 6kmph) represent the speeds traveling 63km and 72km respectively

total time of trip 3hr. t = D/r

63/x + 72/(x+6) = 3 |Multiplying each term by x(x+6) so as all denominators= 1

63(x+6) + 72x = 3x(x+6)

63x + 6*63 + 72x = 3x^2 + 18x

3x^2 -117x - 378 = 0 3(x^2 - 39x - 126) = 0

factoring

(x+3)(x-42) = 0

(x+3) = 0 |tossing out negative solution

(x-42) = 0

x = 42kmph, speed of train while traveling 63kmph, the original average speed