What is the instantaneous speed at t=30 minutes on the given graph?

[Zashmar]

Gday mates,

This is my question
I uploaded a picture of the graph.
Calculate the instantaneous speed when t=30 minutes, I have read something about limits but I don't understand and I am getting really frustrated. Please help ;)

PS answer says 45 KLM/hour

 

[SteamKing]

The instantaneous speed is the slope of the distance-time curve at t = 30 min

 

[Zashmar]

That is what I thought... In that case the answer would be 75k/h

 

[haruspex]

That is what I thought... In that case the answer would be 75k/h

No, it's 45kph. Pls explain exactly how you are calculating the slope.

 

[Zashmar]

By finding the gradient of the line the 30 mins corresponds to, it is rise 3 run 4. So gradient is equal to 3/4 or 75klm

 

[haruspex]

By finding the gradient of the line the 30 mins corresponds to, it is rise 3 run 4. So gradient is equal to 3/4 or 75klm

What are the units of each step on the y axis; likewise on the x axis?

 

[Zashmar]

Y axes is kilometers x-axis is hours

 

[lep11]

Y axes is kilometers x-axis is hours

No, x-axis is minutes.

 

[Zashmar]

Yea whoops

 

[haruspex]

Y axes is kilometers x-axis is hours

If the grid lines were km and hours then your 3/4 should have produced 0.75 km/h.
In fact, they're 5km and 5min.