Question

Aiden measures a book with paper strips. It is actually 10 paper strips long, but he gets an answer of 8. What is his mistake ?

Answer 1

I think the best possibility that could lead Aiden's mistake are the following, First, it must be that the length of the paper strips are not the same. Second, it would be that she miscounted the strips. I hope you are satisfied with my answer and feel free to ask for more 

Answer 2

Since no options are provided, there could be several reasons for this.

Among these reasons are:

1- He did not measure from the beginning of the first strip till the end of the last one.

Now, check the attached picture please.

For the measurement to be correct, he should measure from the beginning of the first strip till the end of the last one as represented by the red line.

If he measured otherwise, say for example, from the end of the first strip till the beginning of the last as represented by the blue line, he will be getting the wrong measurement.

2- The strips may be of different width. This would lead to an error in measurement.

3- He might have simply miscounted the strips.

4- He did not follow the precision or accuracy rules stated for the measurements using paper strips (if they were stated)

Hope this helps :)