1510.51 – Stella's Musical Scores


As is well-known, Stella studied piano with the renowned Nadia Boulanger in Paris after World War II. Later, when settled in Amsterdam, she had three shelves of four-hand piano scores from which she choose music to play with her husband Graziano (who needed to practice more). The top shelf contained 1/6 of the scores. The middle shelf contained more than 2/5 of the scores, and the bottom shelf contained only four scores (the thickest ones).

What is the smallest possible number of scores in total that Stella might have kept on these shelves?


Solution

If xx is the total number of scores, then xx is a multiple of 66.

Note that the top and bottom shelves together hold less than 3/5 of the scores:

16x+4<35x,4<(3516)x=18530x=1330x,120<13x,x>9.23. \begin{aligned} \frac{1}{6}x + 4 &<& \frac{3}{5}x,\\ 4 &<& (\frac{3}{5} – \frac{1}{6})x = \frac{18 – 5}{30}x = \frac{13}{30}x, \\ 120 &<& 13x, \\ x &>& 9.23. \end{aligned}

So xx can be as small as 1212, the first multiple of 66 after 9.239.23. Then Stella's shelves, from top to bottom, would hold 2, 6, and 4 scores. Note that

612>25. \frac{6}{12} > \frac{2}{5}.

That’s a decent collection of four-hand piano scores! (Stella wanted Graziano to practice more, but she didn't want to nag. You can check her biography for further information.)