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.

### Statistics:

 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