Question

(a) 9 cm + 2.8 cm = 11.8

To what decimal place should each answer be rounded? How many significant figures does the rounded answer have?

Answer 1

When adding, the number of decimal places that are significant equals the number of significant decimal places in the least precise measurement added.

Here your first measurement has 0 sig dp, and your second has 1, so your final answer has 0 sig dp, or two significant digits in all. It should be written "12. cm" The trailing decimal point is helpful because it indicates clearly to anyone reading that this is a measurement, and you mean that there are no significant digits after the decimal point. If you left out the decimal point, someone might wonder whether that "12" was an exact integer, that you got from some definition or other.

Answer 2

thank you!

Answer 3

12 :)