6. Two pieces of rope have lengths $1 \mathrm{~m}$ and $2 \mathrm{~m}$. Alex cuts the pieces into several parts. All the parts have the same length. Which of the following could not be the total number of parts he obtains?
A 6
B 8
C 9
D 12
E 15
6. B Since all the parts cut are of the same length, Alex will obtain twice as many parts from his 2 metre piece of rope as he does from his 1 metre piece of rope. Hence, the total number of parts he obtains will always be a multiple of 3 , and he can make it any multiple of 3 . Of the options given, only 8 is not a multiple of 3 and so could not be obtained.