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Mice21 [21]
3 years ago
7

On his outward journey, Ali travelled at a speed of s km/h for 2.5 hours. On his return journey, he increased his speed by 4 km/

h and saved 15 minutes. Find Ali's average speed for the whole journey.
Mathematics
1 answer:
den301095 [7]3 years ago
3 0

Answer:

3.08 km/h.

Step-by-step explanation:

We know that,

Speed=\dfrac{Distance}{Time}

Ali traveled at a speed of s km/h for 2.5 hours.

Let d be the distance and t be the time.

2.5=\dfrac{d}{t}

2.5t=d      ...(1)

On his return journey, he increased his speed by 4 km/h and saved 15 minutes. So, distance is d and times is t-15.

4=\dfrac{d}{t-15}

4(t-15)=d      ...(2)

From (1) and (2), we get

4(t-15)=2.5t

4t-60-2.5t=0

1.5t=60

t=40

Put t=40 in (1).

d=2.5(40)=100

So, t=40 and d=100.

Now,

Total distance = d + d = 100 + 100 = 200

Total time = t + t - 15 = 40 + 40 - 15 = 65

So, the average speed is

\text{Average speed}=\dfrac{\text{Total distance}}{\text{Total time}}

\text{Average speed}=\dfrac{200}{65}

\text{Average speed}\approx 3.08

Therefore, the average speed is 3.08 km/h.

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