The word Decimaly is misspelled against Decimally, an adverb meaning "By tens; by means of decimals."
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Decimally has double "ll" is mispronounced as "l"
Remember double 'LL' in between the strings decima & y which should not be misspelled with single 'L'
Wrong Spelling:  decima-l-y 
Correct Spelling:  decima-ll-y 
Find more wrongly spelled words of Decimally to spell it well.