# Chapter 4 - Number Representation and Calculation - 4.4 Looking Back at Early Numeration Systems - Exercise Set 4.4 - Page 241: 23

$1621$

#### Work Step by Step

$M=1000 \\D=500 \\C=100 \\X=10 \\I=1$ Thus, $MDCXXI = 1000+500+100+10+10+1= 1621$

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