SOLUTION: A boy measures a road as being 69.3km long, however, there is a -1% error in this measurement. What is the true length of the road?

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Question 1145441: A boy measures a road as being 69.3km long, however, there is a -1% error in this measurement. What is the true length of the road?
Found 3 solutions by CubeyThePenguin, greenestamps, ikleyn:
Answer by CubeyThePenguin(3113)   (Show Source):
You can put this solution on YOUR website!
true length: (69.3) * 101% = 69.993 km

Answer by greenestamps(13200)   (Show Source):
You can put this solution on YOUR website!

Another hastily composed and incorrect response from tutor @CubeyThePenguin....

An error of -1% in the measurement means the measured length was 99% of the actual length. So the actual length was 69.3/0.99 = 70 (exactly).

The other tutor's calculation was 69.3*1.01 = 69.993, which he rounded off to 70.

The difference between the two answers is small; but in a similar problem where the error was 10% or even 20%, the differences would be significant.

Answer by ikleyn(52809)   (Show Source):
You can put this solution on YOUR website!
.

Let x be the ACTUAL length of the road. Then the problem says x - 0.01x = 69.3 kilometers. or 0.99x = 69.3 kilometers. Then the actual length is = 70.00000000000 kilometers. ANSWER

Solved.

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It is the correct answer and correct treatment of the problem.

The treatment in the post by @CubeyThePenguin is NOT CORRECT.

Notice that his number of    is 69.993 kilometers ------   NOT 70 kilometers.

Also notice that this problem is not about treating of several centimeters or millimeters of the road -

it is about using the Math conceptions properly.

It is why I have written my post.