As to Arabs, I am not sure there were more than some 700,000 even by 1948, and if so then both because of immigration and birth rate, the number in 1881 is probably only some 150-200M if indeed not just 100-120M.
Lets look for better statistics, that one is highly suspect. The 24M Jews looks like just the Zionist yishuv, without the earlier Jewish population. The Arab figure looks like the entire population, incl Christians and Jews and yishuv.
Peters notes that according to the French geographer Vital Cuinet the population of Western Palestine by 1895 had grown to more than 495,000, "of which Muslims numbered roughly 252,000 throughout Western Palestine.
1882: 141,000 "settled" Muslims
1895: 252,000 "settled" Muslims
The above figures for the Muslim population would indicate that their numbers almost doubled in the thirteen years between 1882 and 1895". Peters states that the only variable which could account for the large 1895 figure would be an approx. 82,000 increase by virtue of "Arab" immigration coinciding with the Jewish development (this is assuming a high rate of natural increase) (p. 244 of her book).
the total population when Jewish colonization began (1872-882) was between 300,000 and 400,000 souls, according to the most reliable estimates. Thirty-four thousand were Jews, living largely in their four "holy cities." Less than half the population was "settled" Muslim, 65,000 were Bedouin-nomadic, and roughly 55,000 were Christians. Thus the total of roughly 200,000 Muslims were living in all of Western Palestine in 1882.
On the installation of Hussein as Emir the population of Jordan dropped by an estimated 30-50% due to emigration to the West Bank where there was much more economic opportunity and the fear of harsh rule and taxation by the new Hashemite rulers.