To simplify 5.2 + 2.1(4.5 - 4 1/7 ), josie argued that it would be easiest to rewrite the mixed number as a decimal since the other three numbers are decimals. do you agree with josie? explain why or why not.

5.2, 2.1 and 4.5 "terminate."  They are rational numbers.  On the other hand, 1/7 is a proper fraction, but its decimal equivalent does not terminate:  0.142857142

It would be faster to approximate the answer by converting 1/7 to a decimal fraction and round off the final result to 1 decimal place.

Certainly we could rewrite the original expression  5.2 + 2.1(4.5 - 4 1/7 )  as

5 2/10 + (2 1/10)*(4 1/2 - 4 1/7), find the LCD, and then go through the indicated operations, to obtain an "exact" answer.  But given that all of the original numbers are given to only 1 decimal place, it makes no sense to worrry about accuracy to 2, 3, 4 or more decimal places.  I'm with Josie.