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

Answer:

80 mph

Step-by-step explanation:

$\boxed{\sf Distance=Speed \times Time}$

First leg of trip

• Speed = 64 mph
• Time = 3 hours

$\implies \sf Distance =64\times 3 = 192\:miles$

Second leg of trip

• Speed = 92 mph
• Time = 4 hours

$\implies \sf Distance=92 \times 4 = 368\:miles$

$\boxed{\sf Speed=\dfrac{Distance}{Time}}$

To find the average speed:

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