Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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Problem K. 532. (January 2017)

K. 532. Greg charges the battery of his cell phone every night, so he can start every new day with a 100% charged battery. If he only uses the phone for talking, the battery lasts 30% longer than when he plays games with it, and it lasts 60% longer than when he is surfing the net. Today, he has talked for 20 minutes on the phone, played for 50 minutes, and spent 80 minutes on the net. The battery is now flat. How long may Greg use the internet with his phone if it is fully charged, and he does not use it for anything else?

(6 pont)

Deadline expired on February 10, 2017.


Sorry, the solution is available only in Hungarian. Google translation

Megoldás. Gergő a mai napot tekintve \(\displaystyle 20 + 1,3\cdot50 + 1,6\cdot80 = 213\) percig tudott volna beszélni. Ezt osztva 1,6-del kapjuk meg azt, hogy egy teljesen feltöltött telefonnal mennyi ideig tud internetezni: \(\displaystyle 213:1,6=133,125\) percig.


Statistics:

81 students sent a solution.
6 points:67 students.
5 points:8 students.
4 points:5 students.
3 points:1 student.

Problems in Mathematics of KöMaL, January 2017