Rounding decimals

Rounding is a decision made by a single digit: the one just to the right of the place you keep. Five or more, the kept digit goes up; four or less, it stays. That holds whether the place is tenths or ten-thousandths.

The page tests the rule where it bites. In 356.79129, rounding to the nearest ten-thousandth means looking at the 9 in the fifth place, which turns 356.7912 into 356.7913. In 4,501.00102, the nearest hundredth keeps its zeros: 4,501.00, not 4,501. Those zeros are rounding to the hundredths place done right, since they show how precise the number is.

The standard is 5.NBT.A.4: use place value understanding to round decimals to any place.

Read question 4 together: 0.15610 to the nearest tenth. Many kids write 0.1 because they see a 1 in the tenths place and stop there. Ask, "Who lives next door to the tenths?" The 5 in the hundredths place pushes it up to 0.2.

Question 6 catches the opposite habit. 5.001 has plenty of digits, but the tenths digit is 0, so the answer stays 5.

In the choice section, have your child underline the digit being kept before ticking a box. For 0.9017 to the nearest thousandth, the underline lands on the 1, and the 7 beside it lifts it to 0.902. The word Hundreth on both pages is a misspelling of hundredth.

Gas station signs often show three decimal places, like 3.459 dollars a gallon. Ask your child to round that price to the nearest cent, then to the nearest dollar, and compare how far each one moved.

On game night, add a house rule to Monopoly: every rent payment gets a 10 percent tip for the bank, rounded to the nearest dollar. A rent of $26 becomes 28.6, which rounds to 29.

Name the work: "You looked one digit to the right every single time." The next sheet, decimal number lines, places numbers like these on a line, so your child can see which neighbor each one sits closer to.