Please can someone help!

51 mph

Step-by-step explanation:

→ The first thing we need is a formula which links speed, distance and time so,

Speed = Distance ÷ Time

Speed = mph

Distance = metres/miles

Time = hours

→ Since we want to work out the average speed of the entire journey we need to first work out the total distance and total time. Using the first sentence of the paragraph, it says that the car travels at an average speed of 45 mph for 40 minutes, we can rearrange the formula to work out the distance so,

Speed = Distance ÷ Time

→ Rearrange to get distance as subject

Distance = Speed × Time

→ Substitute in the values

Distance = 45 × 40

→ Remember that the time is hours but we substituted in minutes so we divide the time value by 60

40 ÷ 60 = 0.666666667

→ Substitute in the time value multiplied by the speed

Distance = 45 × 0.666666667 = 30

⇒ 30 metres/miles is overall distance for the first part of the journey

→ Now we have to work out the distance for the second part of the journey. State the distance formula.

Distance = Speed × Time

→ Substitute in the values into the distance formula

Distance = 60 × 25

→ Remember that the time is hours but we substituted in minutes so we divide the time value by 60

25 ÷ 60 = 0.416666667

→ Substitute in the time value multiplied by the speed

Distance = 60 × 0.416666667 = 25

⇒ 25 metres/miles is overall distance for the second part of the journey

→ Now we have to add the distance of both the journeys together

25 + 30 = 55

→ Then we add the times of the journey together

40 minutes + 25 minutes = 65 minutes

→ Convert 65 minutes into hours

65 ÷ 60 = 1.08333 hours

→ Substitute both values into the speed = distance ÷ time formula

Speed = 55 ÷ 1.08333 = 50.76923077

→ The question says to round it to the nearest whole number so,

50.76923077 = 51 mph

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204