Date post: | 29-Dec-2015 |
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Estimating Square Roots to the Tenths and Hundredths Place
Review
• Yesterday we discussed estimating square roots between two integers and discussed how to improve our estimate to the tenths place.
• Estimate the square root of 3
• At this point, we have to make an educated guess and calculate the squares of rational numbers which include decimals
– You should notice that the square root of 3 is most likely larger than 1.5
• 1.5² = 1.5 x 1.5 = 2.25
• 1.6² = 1.6 x 1.6 = 2.56
• 1.7² = 1.7 x 1.7 = 2.89
• 1.8² = 1.8 x 1.8 = 3.24
• Where would you place , , and ?
– Would you estimate the to be more or less than 2.5?
• Estimate to the tenths place.
• Estimate the to the tenths place
Think Pair Share
• Estimate to the tenths place
Discussion
• How could we improve the estimate to the hundredths place?
Converting Repeating Decimals to Fractions
This Gets a Little Complex
• As we go through a few examples, I want you to look for patterns.
Multiplying by a power of 10
• What happens to my decimal any number every time I multiply by ten?
– Start with the number 8.0
What About This
0.0034
Repeating Decimals
• We need to get the entire portion of the decimal that repeats to the left side of the decimal place
• To do this we will multiply each side by a power of ten until this is accomplished
Repeating Decimals• Lets look at 0.4• We will make x = 0.4
• If I multiply both sides by 10 I get: 10x = 4.4 which can break into 10x = 4 + 0.4 x = 0.4 so I can substitute 10x = 4 + (x)
• Now I need to get one of the variables isolated• 10x – x = 4 + x – x therefore 9x = 4
x =
0.818181…….
• Let x = 0.81
• 100x = 81.81 or 100x = 81 + 0.81
• 100x = 81 + x
• 100x – x = 81 + x – x therefore 99x = 81
x =
0.234234234…..
x = 0.234
1000x = 234.234 or 1000x = 234 + 0.234
1000x = 234 + x
1000x – x = 234 + x – x therefore 999x = 234
x =
Do You See the Pattern?
• Can you do this mentally yet?
– What is the fractional equivalent of 0.434343….?
• Why might it be important to be able to convert a repeating decimal to a fraction?
Exit
• Find the fractional equivalent:
– 1) 0.77777…..
– 2) 0.527527……
– 3) 0.91269126…….