Since the 6 is to the left of the decimal point, that means it's a whole number, and the 52 being to the right of the decimal point means it's not. Also, the number of digits to the right of the decimal tells you if it's tenths, hundredths, thousandths, etc. So 6.52 in words is six and fifty-two hundredths.
If you keep this in mind it should help:
One number to the right of the decimal is tenths, since there is 1 zero in 10.
Two numbers to the right of the decimal is hundredths, since there are 2 zeros in 100.
Three numbers to the right of the decimal is thousandths, since there are 3 zeros in 1,000.
Four numbers to the right of the decimal is ten thousandths, since there are 4 zeros in 10,000.
Five numbers to the right of the decimal is hundred thousandths since there are 5 zeros in 100,000.
And so forth.....
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