Mathematical and Physical Journal
for High Schools
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Problem K/C. 703. (October 2021)

K/C. 703. In a positive decimal fraction, the decimal point is shifted four places to the right. The resulting number is four times the reciprocal of the original number. What is the original number?

(5 pont)

Deadline expired on November 10, 2021.


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

Megoldás. Jelöljük a számot \(\displaystyle n\)-nel. A tizedesvessző 4-gyel való jobbra tolása \(\displaystyle 10\,000\)-rel való szorzást jelent, így \(\displaystyle 10\,000n = 4/n\), ahonnan \(\displaystyle n^2 = 4/10\,000\), \(\displaystyle n = 2/100 = 0,02\).


Statistics:

287 students sent a solution.
5 points:224 students.
4 points:14 students.
3 points:2 students.
2 points:7 students.
1 point:5 students.
0 point:3 students.
Unfair, not evaluated:7 solutionss.
Not shown because of missing birth date or parental permission:6 solutions.

Problems in Mathematics of KöMaL, October 2021