## Stony Brook University

MAT 118 Spring 2013

### Assignment 9 due in Recitation, week of April 8

A. Prime numbers
- Mindscape 8 page 81
- Mindscape 11 page 81
- Mindscape 14 page 81. (The
*Goldbach Conjecture*
is stated on page 80).
- Mindscapes 23, 24, 25 page 82.

B. Clock arithmetic and check digits
- Find two barcodes and study the UPC numbers. Check
that the sum $3d_1+d_2+3d_3+d_4+3d_5+d_6+3d_7+d_8+3d_9+d_{10}+3d_{11}+d_{12}$
is always a multiple of $10$ ("equivalent to $0$ mod $10$"). Explain
carefully why any missing number can be restored if the other eleven
are known. Show for one of your barcodes how $d_2$ can be retrieved if
it is missing.
Same for $d_3$.
- Mindscapes 1, 2, 3, 4 page 92. "Reduce $7$ mod $3$" means
give the remainder when $7$ is divided by $3$. Equivalence is
discussed on page 88.
- Mindscapes 27, 28, 29 page 95.

Remember: Collaboration is fine, but
what you hand in *should be your own work.* Handing in
something you copied is plagiarism and will cost you if it is
detected. Write down what you tried and how it worked.