Comparing and Rounding Decimals
Comparing Decimals -
1. Write decimals in column (lining up decimal points)
2. Add zeros as place holders (if needed) so that each number has the same number of digits
3. Compare digits from left to right
18.781 ___ 18.7081
1. 18.7810 2. A zero was added to make sure there were the same number of digits
18.7081
3.
Because 8 > 0, 18.781 > 18.7081
To make a miniature truck, you need tires with a diameter between 1.465 cm and 1.472 cm. Will a tire with a diameter of 1.4691 cm work? Explain why or why not.
(Classwork Video)
Five runners are entered into a sprinting competition. Four runners have finished the competition. Their scores are 7.8s, 7.65s, 7.69s, and 7.92 s. What score must the last runner get in order to win the competition?
(Classwork Video)
Rounding a decimal definition: To round a decimal means to shorten a decimal to a certain place value and round up or down to that nearest place value.
Example 1:
Round 9.237 to the nearest tenth.
Find the tenths position. 9.237
Look at the digit to the right to decide if you will round up or down. 9.237
If the digit is less than 5, round down. If the digit is 5 or greater, round up.
We will either round this number down to 9.200 or up to 9.300. Round down because the 3 in the hundredths place is less than 5, so round the 2 in the tenths place to 2.
Answer: 9.2 (9.200 = 9.2)
Example 2:
Round 9.237 to the nearest hundredth.
Find the hundredths position. 9.237
Look at the digit to the right to decide if you will round up or down. 9.237
If the digit is less than 5, round down. If the digit is 5 or greater, round up.
This number will either round to 9.230 or 9.240. Round up because the 7 in the hundredths place is greater than 5, so round the 3 in the hundredths place to 4.
Answer: 9.24
What is a decimal number of millions?
We can use decimals to represent larger numbers. For instance, the number 1,250,000 can be rewritten as 1.25. The new number is written as a decimal number of millions.
The table below charts different types of natural disasters in 2012, and the amount of property damage for each. Complete the table by rounding each number to the nearest hundred thousand, change the property damage to a decimal number of millions, and create a bar graph to display the data. What conclusions can you make about the data?
Source: http://www.nws.noaa.gov/om/hazstats/sum12.pdf
Guided Practice:
1. In the 2012 London Olympics, the top 5 women's jumps were: 6.77 6.88 7.12 6.89 7.07
Place them in winning order, with the longest jump first.
2. Write 4 decimals between 4.8 and 4.9 in order of least to greatest.
3. At a random sampling of gas stations, one gallon of gas cost 3.61 3.81 3.63 3.74 3.63
Write the prices in order from lowest to greatest.
4. If you divide a mile (5,280 feet) into 13 equal sections, each section is 406.153846154 feet long.
If you round to the hundredths place, how many feet are in 1/13 of a mile.
5. A chemical compound melts at 176.587 degrees Fahrenheit. Round the melting point to the nearest tenth.