In their 30s
30 (apex)
30s
physical strength peaks between 25 and 35 years of age.
A person's metabolism is expected to drop 3-5% for each decade lived.
During the first decade of 1800, on Dec.2,1804.
During the first decade of 1800, on Dec.2,1804.
1970s
During the first decade of the last century.
During the 1990's.
I assume you are looking at bode plots. 20dB per decade means an increase or decrease in signal strength of 20dB for every decade of frequency (10Hz to 100Hz is a decade, 100 Hz to 1000Hz is a decade). This is common talk when discussing filters. If you want further (graphical) explanation, search wikipedia for "bode"
There was not a set curriculum for education in the 1930s. Arithmetic, reading and grammar were taught, and during this decade, non-academic classes, such as physical education were beginning to enter schools.
1920s