Question

A bus travels first 120km of a trip at a speed of 40km per hour .What should be the speed for the next 480km so that average speed of the bus is 60km/hr?
answer asap pls

Answer 1

Answer:

• Distance = 120+480 = 600 km
• Distance travelled with a speed of 40 km/h speed = 120 km
• Average speed = 60 km/h
• Speed for the distance 480 km = ?

$\displaystyle\underline{\bigstar\:\textsf{According to the given Question :}}$

$\displaystyle\sf :\implies Speed = \dfrac{Distance}{Time}$

$\displaystyle\sf :\implies Time = \dfrac{Distance}{Speed}$

$\displaystyle\sf :\implies T_1 = \dfrac{120}{40} = 3 \ hrs$

$\displaystyle\sf :\implies T_2 = \dfrac{480}{x}$

• Then now that we have the Total distance, the speed and the time taken then if we substitute these values on the formula to find Average Speed we will get our Answer assuming x as the speed

$\displaystyle\sf \dashrightarrow Avg \ Speed = \dfrac{Total Distance}{Total Time}$

$\displaystyle\sf \dashrightarrow 60 = \dfrac{600}{T_1+T_2}$

$\sf \dashrightarrow 60 = \dfrac{600}{3+\frac{480}{x}}$

$\displaystyle\sf \dashrightarrow 60 = \dfrac{600}{\dfrac{3x+480}{x}}$

$\displaystyle\sf \dashrightarrow 1 = \dfrac{10x}{3x+480}$

$\displaystyle\sf \dashrightarrow 3x+480 = 10x$

$\displaystyle\sf \dashrightarrow 3x-10x = -480$

$\displaystyle\sf \dashrightarrow -7x = -480$

$\displaystyle\sf \dashrightarrow x = \dfrac{-480}{-7}$

$\displaystyle\sf \dashrightarrow\underline{\boxed{\sf x = 68.5 \ km/h}}$

$\displaystyle\therefore\:\underline{\textsf{ The speed for the 480 km will be \textbf{ 68.5 km}}/\textsf{\textbf{h}}}$