1. Rounding Numbers – Part 2 Slideshow 2, Mr Richard Sasaki, Room 307

2. Objectives Understand the meaning of significant figuresUnderstand the meaning of significant figures Be able to write large or small numbers in standard index formBe able to write large or small numbers in standard index form Be able to round and calculate with such numbersBe able to round and calculate with such numbers

3. Rounding Let’s have a quick review. The nearest 2 decimal places 74.75 The nearest 1 decimal place 74.8 The nearest integer 75 This is a common way to round numbers with decimals. Next we’ll look at rounding with significant figures.

4. Significant Figures If we see a number like 4,458,327,732 it doesn’t look very nice. It may be that some of those digits aren’t very significant so we can simplify it a bit. When we found a number to __ significant figures, we rewrite that number to only show interest in those figures. Examples Write 347 rounded to 2 significant figures. 350 Write 75,321 rounded to 3 significant figures. 75,300

5. Significant Figures We can also do this with small decimal numbers. Examples Write 5.329 rounded to 3 significant figures. 5.33 Write 0.00593 rounded to 1 significant figure. 0.006 Any zeroes at the start or end of big or small numbers do not count towards significant digits. 0.0005003 (4 s.f) 53,000,000 (2 s.f)

6. Answers 4 428,000 430,000 400,000 6 0.00048232 0.000482 0.0005 9.392 9.4 9 483900480000500000 27360 27000 30000 837.2 840 800 50.00 50 50 45.50 45 50 100.00 100 100 124000120000100000

7. Standard Form Standard (index) form comes from index form. If we write a number in index form, we write it in the form… Writing numbers in standard form is very useful and important for huge or tiny numbers. You will see numbers in this style in physics and social studies too. But what is it?

8. Standard Form To write a number in standard form, we split it into two components. I’ll use the number 741,200,000,000 for the example. This number contains all significant figures. It always has the units figure on the left!

9. Examples Let’s write the following in standard form. 3,500,000,000 74,000,000,000 82 7,530 0.004 0.00392 Try the worksheet!

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