1. 1 EstimationStrategies Press Ctrl-A ©2009 – Not to be sold/Free to use Stage 5 Year 9

2. 2 End of Slide Level of accuracy - approximation When find the area of a circle the 8 decimal places on the calculator may not be relevant. r = 2.9cm A =  r 2 A =  x 2.9 2 A Upper =  x 3.0 2 A Lower =  x 2.8 2 = 26.420794 = 28.274333 = 24.630086 More than 2 significant figures - meaningless. = 26 Use the significant figures in question.

3. 3 End of Slide Level of accuracy - approximation Find the area of the square. 2.75 m Three significant figures Area = s 2 = 2.75 2 = 7.5625 = 7.56 cm 2

4. 4 End of Slide Level of accuracy - approximation Find the area of the square. 17.05 m Four significant figures Volume = s 3 = 17.05 3 = 4956.477625 = 4956 cm 3