Problems of the Week

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2017-12-11 Intermediate


In the regular decagon below, find the percentage of area that is shaded orange.

\[ ab = a^2+b^2 \] It is obvious that \(a=b=0 \) satisfies the equation above. But is there another pair of real numbers \((a,b)\) satisfying this equation?

A slackline is stretched between two trees at a distance, \(d = 10\,\text{m}\), so that a tensioning force, \(F_0 = 5000 \,\text{N}\), is applied on the empty rope. A man then balances in the middle of the rope and exerts a weight force, \(F_g = 750 \,\text{N}\), onto the slackline. What is the vertical deflection, \(h\), of the rope?

Details and Assumptions: The rope is made of an elastic material and obeys Hooke's law \(F = K \frac{l - l_0}{l_0},\) where \(F\) is the force along the rope, \(l_0\) is the initial length, \(l\) is the stretched length of the rope, and \(K = 150\text{ kN}\) is the force constant.

You have a set of 10 paints of distinct colors and a flag with 5 regions, shown to the right.

In how many ways can you color all 5 of the regions such that regions that share an edge are different colors?

Note: The flag is attached to a flagpole, which prevents the flag from being rotated or flipped.

What is the minimum number of soldiers needed to form \(12\) lines of at least \(3\) soldiers each?

6 soldiers can form 3 lines of 3 soldiers each

6 soldiers can form 3 lines of 3 soldiers each

Note: The lines must be distinct. For example, if you have 5 soldiers in a line, this only counts as 1 line.


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