Question

The odometer shows a palindromic number, a number that is the same written forwards and backwards. Two hours later the number is palindromic again. How fast was the car going, if the first number was 15,951 miles?

Answer 1

55 MPH.

Here's my thinking.

I started with the premise that an average speed is about 60 MPH. Well, that means in one hour, you would have driven 60 miles. In another hour, that's 120 miles. So, I added 120 to 15,851.

15, 951

+   120

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16, 071

But, I'm looking for a palindromic number that's close to that. And, sure enough, there IS such a number: 16, 061.

That would mean that you traveled 110 miles:  (16,061 - 15,951)

Plug this data into the formula:   S = D/T  (Speed = distance divided by time)

S = 110/2

S = 55 (MPH)

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Pretty cool, huh?