Decimal notation is an easy way to represent fractions with denominators of 10 or 100. Solving problems using decimal numbers can be much easier than solving those same problems using fractions.
To better understand decimals…
LET’S BREAK IT DOWN!
Let’s say you want to make cheesy sticks for a party and you need 12 [ggfrac]3/10[/ggfrac] loaves of bread. You can represent that number with a decimal. You know how to write 12 with a 1 in the tens place and a 2 in the ones place. You can put a decimal point after the 2 in the ones place. The next place to the right is the tenths place. You can write 3 in the tenths place to represent 0.3. 12.3 is 12 310 written as a decimal. Try this one yourself. To double the cheesy stick recipe, you need 24 [ggfrac]6/10[/ggfrac] loaves of bread. How can you represent that number with a decimal?
Let’s say you want to compare the weights of your two pet mice. One mouse weighs 129.3 grams. The second mouse weighs 129.5 grams. You can use place value to compare those two numbers. Start at the greatest place to compare. Both numbers have 1 in the hundreds place, 2 in the tens place, and 9 in the ones place. To find which number is greater, compare the digits in the tenths place. 5 tenths is greater than 3 tenths, so 129.5 grams is greater than 129.3 grams. Try this one yourself. One of April's pet mice weighs 127.4 grams. The other mouse weighs 127.1 grams. Which mouse is the heaviest?
Let’s say you and your friend enter a cup-stacking contest. It takes you 9.04 seconds to stack the cups. It takes your friend 9.26 seconds to stack the cups. Who won the contest? First we compare the ones. 9 = 9, so we compare the tenths: 0 < 2. So, 9.04 < 9.26. You took less time, so you won the contest. Try this one yourself. It took April 10.53 seconds to stack the cups. It took Marcos 10.06 seconds to stack the cups. Who took the least amount of time to stack the cups?
Let’s say Jill and Niko run an obstacle course. The record at the course is 16.3 seconds. Jill ran the course in 16.37 seconds. 16.3 has 0 hundredths. 16.37 has 7 hundredths. So, 16.37 > 16.3. Jill did not break the record. Niko runs the course in 16.29 seconds. 16.29 has 2 tenths, which is less than 3 tenths. 16.29 < 16.3. Niko broke the record. Try this one yourself. Another course has a record time of 14.02 seconds. You ran that course in 14.2 seconds. Did you break the record?