Use place value understanding to round decimals to any place.
Official wording from the Common Core State Standards for Mathematics (Β© 2010 National Governors Association Center for Best Practices and Council of Chief State School Officers). View on thecorestandards.org
Rounding a decimal means finding the closest number that stops at a chosen place. To round 3.76 to the nearest tenth, students ask which two tenths it sits between (3.7 and 3.8) and which one it is closer to. Since 3.76 is 6 hundredths past 3.7 and only 4 hundredths short of 3.8, it rounds to 3.8.
The expectation is that students understand rounding through place value and position, not only through a rule about looking at the next digit. A number line marked with the two candidate values and the halfway point (3.75 in this case) makes the decision visible. Rounding to any place, whole numbers, tenths or hundredths, uses the same thinking, and the same reasoning works for thousandths when a measurement calls for it. Students also need to keep the place they rounded to, so 4.96 rounded to the nearest tenth is written 5.0, which shows the rounding was to tenths.
When rounding to the nearest tenth, the deciding digit is the hundredths digit. Students who check the thousandths digit get answers that are not the closest tenth.
Rounding 2.449 first to 2.45 and then to 2.5 gives the wrong tenth. The number is closer to 2.4, so it must be rounded in one step.
Some students round 8.34 to the nearest tenth and write 8.4 because 'the 4 makes it go up'. 4 hundredths is less than halfway, so it stays 8.3.
Writing 9.98 rounded to the nearest tenth as 10 hides the place value. 10.0 shows the answer is correct to the nearest tenth.
Round 14.358 to the nearest whole number, the nearest tenth and the nearest hundredth.
Answer: 14 (whole number), 14.4 (tenth), 14.36 (hundredth).
Begin with vertical number lines showing just the two candidate values and the midpoint. Ask students to place the decimal and say which end it is closer to. Once that reasoning is secure, the 'look at the next digit' shortcut makes sense as a description of where the number sits relative to the midpoint.
Items often present a decimal and ask for it rounded to a named place, or ask which of several decimals round to the same value. Money contexts, such as rounding a price to the nearest dollar, are common.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: 7.5
7.46 is between 7.4 and 7.5. The halfway point is 7.45 and 7.46 is above it, so it rounds to 7.5.
Answer: 12.83
12.831 is between 12.83 and 12.84. The thousandths digit 1 puts it below the halfway point 12.835, so it rounds to 12.83.
Answer: A) 6
5.62 is between 5 and 6, and it is past the halfway point 5.5, so it rounds to 6.
Answer: D) 3.249
3.249 is between 3.2 and 3.3, and it is below the halfway point 3.25, so it rounds to 3.2. 3.14 rounds to 3.1, while 3.25 and 3.27 round to 3.3.
Answer: 10.0 (also accepted: 10)
9.96 is between 9.9 and 10.0, closer to 10.0. Writing 10.0 shows the answer is to the nearest tenth.
Answer: B) 13.48 cm
13.475 is exactly halfway between 13.47 and 13.48. By the usual convention a number at the halfway point rounds up, so the answer is 13.48 cm.
A full lesson with slides, activities and an exit ticket on rounding decimals, pitched to grade 5 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on 5.NBT.A.4 with an answer key, ready in about a minute.
Make a worksheet βTurn rounding decimals into a quiz students answer online that marks itself, with a class summary for you.
Build a test βThe usual school convention is to round up, so 2.45 rounded to the nearest tenth is 2.5. Students should know this is a convention rather than a closer value.
Both have the same value, but 7.0 communicates that the rounding was to tenths, which is usually what a question is checking.