Chapter 5.2, Problem 4P

Run used a calculator to determine that

$0.35\times 2.4=0.84$

He wants to know why the rule about adding up the number of places to the right of the decimal point doesn’t work in this case. Why aren’t $2+1=3$ digits to the right of the decimal point in the answer? Is Ron correct that the rule about adding the number of places to the right of the decimal points is not correct in this case? Explain.