HoffyEd ← Decimals

Rounding Decimals

Rounding swaps an exact number for a simpler one that's close by. Find the two neighbors, pick the closer one, and you're done.

Start with the Rounding Hill below. Already a pro? Take the 60-second challenge or jump to practice.

1

Closer to Which Neighbor?

People round all the time when an exact number is more than they need.

12.468 seconds
12.5 s
on the scoreboard
$3.479 a gallon
$3.48
to the nearest cent
$24.89
about $25
to the nearest dollar

Every decimal sits between two neighbors at the place you're rounding to. 4.37 sits between 4.3 and 4.4. Rounding means picking the neighbor that's closer. Think of a hill between the two neighbors: wherever the ball sits, it rolls down toward the closer side.

The Rounding Hill
Drag the ball, then let go. Which way does it roll?
Keyboard: focus the ball, use ← → to move it, and press Enter to let it roll.
Right on top? A number exactly halfway between the neighbors, like 4.35, is just as close to each side. The rule everyone agrees on: halfway rounds up. So 4.35 rounds to 4.4.
2

Round in Three Steps

You won't always have a hill to look at. These three steps give the same answer every time.

1
Find the rounding place. Spot the digit in the place you're rounding to.
2
Look next door. Check the one digit just to its right. That digit decides.
3
5 or more? Round up. Less than 5? Keep it. Then drop every digit after the rounding place.
The Step Machine
Press Next step to watch the rule work, one step at a time.

Tricky Cases

Exactly 5
6.25 → 6.3
Nearest tenth. Next door is a 5, and 5 means round up.
The 9 rolls over
3.97 → 4.0
Nearest tenth. The 9 can't become 10 in one place, so it becomes 0 and the ones digit goes up. Keep the 0 — 4.0 shows you rounded to tenths.
Don't round twice
2.348 → 2.3
Nearest tenth. Only the digit next door counts, and it's a 4. Rounding to 2.35 first, then to 2.4, gives the wrong answer.
Money
$5.678 → $5.68
A cent is one hundredth of a dollar, so nearest cent means nearest hundredth.
3

Round It! 60-Second Challenge

Each number shows its two neighbors. Tap the one it rounds to. How many can you get in a minute?

Round to the nearest
4

Let's Practice

Three activities. Aim for 8 out of 10 or better on each to show you've mastered rounding.

Pick the Rounded Number

Choose the correct answer. Watch for the tricky cases!

Question 1 of 10Score: 0

Type It In

Round the number and type your answer.

Question 1 of 10Score: 0

Real-World Rounding

Times, prices, weights, and more. Read carefully to find the rounding place.

Problem 1 of 8Score: 0
Nice work! Rounding is the first step to estimating with decimals. Head back to the Decimals hub to keep going.