Do Now: 47° 6.2m x θ 16cm 13cm 5.8m 54.3°
Rounding Decimals How many decimal places do each of these numbers have?
Rounding Decimals When rounding decimals: keep the required number of decimal places if the next digit is < 5 (less than 5) keep the final required digit the same and drop all the unwanted digits off if the next digit is ≥ 5 (greater than or equal to 5) round up by adding 1 to the final required digit and then dropping off all the unwanted digits.
Examples Round the following decimals to the number of decimal places indicated in the brackets a) (1 dp) b) (3 dp) c) (2 dp) d) (3 dp) When solving a problem the answer should always be rounded to a sensible number of decimal places. The number of decimal places a number is rounded to should be written in brackets after the answer.
A 150cm plank of wood is divided into seven pieces. How long is each piece? cm It would be sensible to round this answer to 1dp or 2dp.
Recap of rounding decimals 1)Round to 2dp 2)Round to 2dp 3)Round to 3dp 4)A family uses 3578 litres of water in one week. How much water does the family use, on average, per day? (Round your answer to the nearest litre) 5) Here are the rainfall amounts for the five months of May, June, July, August and September. 59.3cm, 18.28cm, 25.91cm, cm and 18.4cm What is the total rainfall for this five-month period? L 201.2cm
Significant Figures How many significant figures do these numbers have:
Zeros are significant when they are: inbetween other numbers Both at the end of a number and after the first non-zero digit after the decimal place. Examples: (4sf) (4sf) Zeros are not significant when they are: At the front of a number At the end of a number with no decimal point Examples: (2sf) (2sf) When rounding, using significant figures, it is often necessary to use zeros as place holders.
Examples Round 389 to 1 significant figure Round 2136 to 1 significant figure Round 47 to 1 significant figure Round 6451 to 2 significant figures
More examples.... Round to 2 significant figures Round to 1 significant figure Round to 3 significant figures
Some for you to try: 3556 (1sf) 4368 (2sf) (1sf) (2sf) 1843 (2sf) (4sf) Ticks worksheet L6 P3 pg 19