I recently got this peculiar interview question, and I wanted some help figuring out how to reach an appropriate solution. Imagine that we have a race car that is driving on a 50-mile-long race track, and this race car has five minutes to drive along this race track. Suppose that I went 20 miles per hour on the first half of the race track. How fast do I need to go on the second half of the race track such that I average 40 miles per hour over the whole drive on the track?I immediately went for the idea that the answer was 60 miles per hour, but supposedly that was wrong. I think I needed to better consider the fact that miles per hour is a measure of distance over time. So 40 mph = 40 miles 60 minutes ,But I am now stuck on how to use this information to deduce how many minutes I need to take on the second half to average this speed. Any suggestions?

Question

I recently got this peculiar interview question, and I wanted some help figuring out how to reach an appropriate solution. Imagine that we have a race car that is driving on a 50-mile-long race track, and this race car has five minutes to drive along this race track. Suppose that I went 20 miles per hour on the first half of the race track. How fast do I need to go on the second half of the race track such that I average 40 miles per hour over the whole drive on the track?I immediately went for the idea that the answer was 60 miles per hour, but supposedly that was wrong. I think I needed to better consider the fact that miles per hour is a measure of distance over time. So  40  mph  =            40       miles              60       minutes        ,But I am now stuck on how to use this information to deduce how many minutes I need to take on the second half to average this speed. Any suggestions?

Carmelo Payne · Accepted Answer

We have       v    1    =  20  ,      d    1    =  25  ,      d    2    =  25We want   40  =                              d          1                +                  d          2                                      d          1                          /                          v          1                +                  d          2                          /                          v          2                      =            50              25                  /                20        +        25                  /                          v          2                     (that is: total distance divided by total time).Hence we need indefinite speed.       v    2    =            25              50                  /                40        −        25                  /                20              =            25      0

kokoszzm · Accepted Answer

This wouldn&#039;t work. The first 25 miles he does it at 20mph. It would take him over an hour so its over the 5 minutes.

I recently got this peculiar interview question, and I wanted some help figuring out how...

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