Significant Figures The amount of significant figures in a number tells us how accurate the number is. When we look at a number we should treat all figures as significant unless they are zeros at the start of a decimal. Ex sig figs Ex sig figs Ex sig figs

Timed Exercise - How many Sig Figs In? 1) ) ) ) ) ) ) )

FOR DISCUSSION - DON’T COPY !!!! The number 4587 has 4 sig figs ie Th, H, T & U If we round this to two sig figs thenwe lose the T & U. So 4587 becomes4600

FOR DISCUSSION - DON’T COPY !!!! The number has 5 sig figs ie Th, H, T, U & t If we round this to three sig figs thenwe lose the U & t. So becomes3460

Example 1Round to two sig figs This has 4 sig figs = 230 Example 2Round to three sig figs This has 6 sig figs = Example 3 Round to two sig figs This has 4 sig figs =

Round each of the following to two significant figures.. TIMED EXERCISE 2 1) ) ) ) ) ) ) )

One Sig Fig Approximations By rounding numbers to one sig fig we can find approximate answers to calculations Ex X 67.9 X = 400 X 70 X 0.5 = Ex  53.1 = 200  50 = 4

Ex3 Which of the following could be the answer to 19.8 X 5.23  11.3 ? (a) 9276(b) 916.7(c) 93.64(d) X 5.23  11.3 becomes 20 X 5  10 = 10 So answer (d).