Question

A girl has to cover a distance of 400 km in 5 hours.
He traveled for some time at a speed of 85 km/h
and the rest of the time at a speed of 55 km/h. How
long did he travel at high speed?
एक लड़की को 400 km की दूरी को 5 घंटे में तय करना है। उसने कुछ
समय 85 km/h की गति से और शेष समय 55 km/h की गति से
यात्रा की। उसने अधिक गति से कितनी देर तक यात्रा ​

Answer 1

Answer:

4.2 hours

Step-by-step explanation:

Since , the total distance is 400 km.

He will cover the same in 5 hours;

He traveled for some time at a speed of 85 km/hr.

Let that time be t1;

He also traveled for some time at a speed of 55 km/hr

Let that time be t2;

So, according to question , t1+t2=5.......(1)

Now finding t1;

Let the distance for which he covered at the speed of 85 km/hr be x;

So, t1 = x/85;

Let the distance for which he covered at the speed of 55 km/hr be (400-x)

So, t2 = (400-x)/55;

Now, put t1 and t2 in equation (1);

∴ $\frac{x}{85} + \frac{400-x}{55} = 5$

Taking the lcm of 85 and 55 we get 935

∴ $\frac{11x + 17(400-x)}{935} = 5$

By solving above we get , x = 354.2

∴ t1 = $\frac{d}{s} = \frac{354.2}{85} = 4.2$

So, he traveled 4.2 hours at high speed.

Answer 2

• The girl travel for 4 hours , 10 minutes at high speed .

Given :- A girl has to cover a distance of 400 km in 5 hours. She traveled for some time at a speed of 85 km/h and the rest of the time at a speed of 55 km/h .

To Find :-

• How long did she travel at high speed ?

Formula used :-

• Time = Distance ÷ Speed .

Solution :-

Let us assume that, the girl cover x km at 85km/h and rest (400 - x) km at 55 km/h .

It is given that, total time is 5 hours .

So,

→ Time taken at covering x km with a speed of 85km/h + Time taken at covering rest (400 - x) km with a speed of 55km/h = 5 hours

since Time is equal to (Distance ÷ Speed) ,

we get,

→ {(x ÷ 85)} + {(400 - x) ÷ 55} = 5

→ (11x + 6800 - 17x) ÷ 935 = 5

→ (6800 - 6x) = 935 × 5

→ 6800 - 6x = 4675

→ 6x = 6800 - 4675

→ 6x = 2125

→ x = (2125/6) km

Then,

→ Total time travelled at high speed (which is 85 km/h) = D/S

→ Required time = (2125/6) × (1/85)

→ Required time = (25/6) { 85 * 25 is equal to 2125 }

→ Required time = 4(1/6) hours

→ Required time = 4 hours + (1/6) * 60 minutes

→ Required time = 4 hours , 10 minutes (Ans.)

Hence, the girl travelled for 4 hours , 10 minutes at high speed .

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