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Investigate polygons with all the vertices on the lattice points of a grid. For each polygon, work out the area A, the number B of points on the boundary and the number of points (I) inside the polygon. Can you find a formula connecting A, B and I?

Weekly Problem 17 - 2013

Stage: 2 and 3 Challenge Level: Challenge Level:1

Anna has $3$ brothers and $5$ sisters. Her brother Tom has $S$ sisters and $B$ brothers.

What is the value of $S \times B$?
 
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.  

This problem is taken from the UKMT Mathematical Challenges.

View the previous week's solution