I always used to tell my students every pilot in the world is born in 1975.
Why they ask me.
Now this is the reason:
Put the numbers vertical:
1
9
7
5
Now change the in
1,0 = 90 degrees
0,9 = 60 degrees
0,7 = 45 degrees
0,5 = 30 degrees.
For a 90 degrees x-wind take the wind speed x 1,0
For a 60 degrees x-wind take the wind speed x 0,9
Etc. etc. etc.
You can do a lot more with it if you turn it around, like calculating your groundspeed and drift correction. But that was not asked for.