Question

Charlotte drives 64 mph for the first 3 hours of her trip and 92 mph for last 4 hours.

She has a "lead foot". What is her average speed for the entire trip? Show your
work.

Answer 1

Please correct me if wrong:
64x3= 192
92x4= 368

192+368= 560

560\7= 80

Correct answer: 80

Answer 2

80 mph

Explanation:

`\boxed{\sf Distance=Speed * Time}`

First leg of trip

• Speed = 64 mph
• Time = 3 hours

`\implies \sf Distance =64* 3 = 192\:miles`

Second leg of trip

• Speed = 92 mph
• Time = 4 hours

`\implies \sf Distance=92 * 4 = 368\:miles`

`\boxed{\sf Speed=(Distance)/(Time)}`

To find the average speed:

`\begin{aligned}\implies \sf Average\:speed & = \sf (Total\:distance)/(Total\:time)\\\\ & = \sf (192+368)/(3+4)\\\\& = \sf (560)/(7)\\\\ & = \sf 80\:mph\end{aligned}`