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K. 315. Let denote the greatest prime number smaller than n, and let denote the smallest prime greater than n. Calculate the value of the expression .

(6 points)

This problem is for grade 9 students only.

Deadline expired on 10 January 2012.

Google Translation (Sorry, the solution is published in Hungarian only.)

Megoldás. $\displaystyle \downarrow\! 35\! \downarrow=31$, $\displaystyle \uparrow\! 53\! \uparrow =59$, $\displaystyle \uparrow\downarrow\! 40\! \downarrow\uparrow=\uparrow\! 37\! \uparrow=41$, tehát a keresett kifejezés értéke $\displaystyle 41+31–59+41=54$.

Statistics on problem K. 315.
 278 students sent a solution. 6 points: 58 students. 5 points: 85 students. 4 points: 93 students. 3 points: 24 students. 2 points: 9 students. 1 point: 2 students. 0 point: 1 student. Unfair, not evaluated: 6 solutions.

• Problems in Mathematics of KöMaL, December 2011

•  Támogatóink: Morgan Stanley