Question

Michelle and Mike are on their way to the mall to shop for their Nana's birthday, but Mike has to stop for a couple of errands first.
If their speeds excluding and including the stoppages are 60 mph and 50 mph, respectively, how early will they reach the mall if Mike doesn't stop at all?

• A. 12.3 minutes
• B. 7 minutes
• C. 9.6 minutes
• D. 5 minutes

Answer 1

The correct option is C 9.6 minutes

Speed excluding stoppages = 60 mph
Speed including stoppages = 50 mph

Thus, the distance covered per hour without any stoppages = 60 – 50 = 10 mi

We know that
$Speed=\frac{Distance}{Time}$

$\Rightarrow Time=\frac{Distance}{Speed}$

Hence, the time taken to cover 10 miles without any stoppages would be:
$Time=\frac{10mi}{60mph}=0.16h$

We know, 1 h = 60 min

∴ 0.16 h = 0.16 × 60 = 9.6 min

So, Mike will reach the mall 9.6 minutes early if he does not stop at all.