24 is only four steps from 20, so it rounds to 20.
The big ideaLook at the ones row. Four or fewer fall back. Five or more slide up.
How it works
Rounding to the nearest ten finds the ten that is closest to a number.
Picture a hill between two tens. A ball on the hill rolls to the nearer ten.
On the frame, look at the ones row. Four ones or fewer slide back, and five or more slide up to the next ten.
Exactly five ones sit halfway, and the rule is that five or more goes up.
24: two tens and four ones. The four ones slide back.Zero to four go back, five to nine go up.
Example 1: 24 rounds to 20
24 is two tens and four ones.
Four ones are few, so they slide back.
The tens stay as 2 tens.
24 rounds to 20.
Example 2: 28 rounds to 30
28 is two tens and eight ones.
Eight ones are many: they slide away and one more ten slides across.
That makes three tens.
28 rounds to 30.
28 rounds up: three tens and no ones.
Example 3: 66 rounds to 70
66 is six tens and six ones.
Six ones are many, so they slide up and make one more ten.
Seven tens is 70.
66 rounds to 70.
Example 4: 75, right on the hill
75 is seven tens and five ones.
Five ones sit halfway between 70 and 80.
Everyone agreed on one rule: five or more goes up.
75 rounds to 80.
Example 5: Sliding on the frame
To round 43 on the frame, slide the ones back: 43 − 3 = 40.
To round 46, slide the ones away and add a ten: 46 + 4 = 50.
Either way the frame ends on a whole ten.
Words to know
round
Find the nearest whole ten to a number.
nearest ten
The whole ten a number is closest to, like 20 or 30.
fall back
Four ones or fewer slide back to the ten below.
slide up
Five ones or more slide away and make one more ten.
Watch out
Only the ones row decides. The tens row picks the village.
Five ones go up, not down.
A rounded number is an about number, like about 30 pears, not the exact count.
On this frame we round to the nearest ten only.
Try it
What does 43 round to?
What does 57 round to?
What does 85 round to?
Does 61 round to 60 or to 70?
Answers: 1. 40 · 2. 60 · 3. 90 · 4. 60
Try at homeAsk a grown-up to help you find three prices, on a receipt or a shop leaflet. For each one, look at the ones and decide: does it fall back to the ten below, or slide up to the next ten? Then say it in a sentence, like 'about thirty'.
For grown-upsFind three prices on a receipt or a leaflet. For each one, look at the ones and say if it falls back or slides up, then say it as a sentence, like about thirty.
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