Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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Problem K. 627. (September 2019)

K. 627. The teacher selects a student from a class at random. The probability of selecting a boy is \(\displaystyle 2/3\) of the probability that he selects a girl. What fraction of the whole class are girls?

(6 pont)

Deadline expired on October 10, 2019.

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

Megoldás. Legyen \(\displaystyle f\) fiú és \(\displaystyle l\) lány az osztályban, ekkor \(\displaystyle \frac{f}{f+l} = \frac{l}{f+l} \cdot \frac23\), azaz \(\displaystyle 3f = 2l\), tehát minden 2 fiúra 3 lány jut, tehát 5 főből 3 lány, így a lányok aránya \(\displaystyle \frac35\) az osztályban.


209 students sent a solution.
6 points:130 students.
5 points:26 students.
4 points:11 students.
3 points:4 students.
2 points:7 students.
1 point:8 students.
0 point:5 students.
Unfair, not evaluated:5 solutionss.
Not shown because of missing birth date or parental permission:13 solutions.

Problems in Mathematics of KöMaL, September 2019