Question

The car travels 30 km at the uniform speed of 40 kilometre per hour and 30 kilometre at the uniform speed of 20 km find the average speed​

Answer 1

The car travels the first 30 km with a speed of 40 km/hr and next 30 km with a speed of 20 km/hr.

We have to find the average speed of the car.

Average speed is defined as the ratio of total distance covered with respect to total time taken.

Total distance covered by the car = Distance covered in first half + Distance covered in second half

= (30 + 30) km

= 60 km

Total time taken (T) = t1 + t1

Now,

Time = Distance/Speed

t1 = 30/40 hr and t2 = 30/20 hr

T = 30/40 + 30/20

T = 3/4 + 3/2

T = (3 + 6)/4

T = 9/4 hr

Average speed = (Total distance covered)/(Total time taken)

= 60/(9/4)

= (60 × 4)/9

= 26.67

Therefore, the average speed of the car is 26.67 km/hr.

Answer 2

Answer:

Given:

• The car travels 30 km at the uniform speed of 40 kilometre per hour and 30 kilometre at the uniform speed of 20 km.

Find:

• Find the average speed.

Calculations:

• Let T be time taken, Let t1 and t2 be time 1 and time 2.

⇒ $\bold{(30 + 30)}$

⇒ ${\sf{\underline{\boxed{\red{\sf{60 \: km }}}}}}$

Using formula:

☆ ${\sf{\underline{\boxed{\green{\sf{Time = \dfrac{Distance}{Speed} }}}}}}$

Step-by-Step:

⇒ $\bold{t1 = \dfrac{30}{40}}$

⇒ $\bold{t2 = \dfrac{30}{20}}$

Note:

☆ ${\sf{\underline{\boxed{\orange{\sf{Time \: taken = \dfrac{t1}{t2} }}}}}}$

⇒ $\bold{T= \dfrac{30}{40} + \dfrac{30}{20}}$

⇒ $\bold{T = \dfrac{3}{4} + \dfrac{3}{2}}$

⇒ $\bold{T = \dfrac{3 + 6}{4}}$

⇒ ${\sf{\underline{\boxed{\green{\sf{T = \dfrac{9}{4} }}}}}}$

Using formula:

☆ ${\sf{\underline{\boxed{\orange{\sf{Average \:speed = \dfrac{Distance \: covered}{Time \: taken} }}}}}}$

Step-by-Step:

⇒ $\bold{\dfrac{60}{ \dfrac{9}{4} }}$

⇒ $\bold{\dfrac{60 \times 4}{9}}$

⇒ ${\sf{\underline{\boxed{\red{\sf{26.67}}}}}}$

Therefore, 26.67 is the average speed of the car.