Grade 3 · Maths · As written
Numbers to a thousand, and rounding them
Read, build and split three-digit numbers, and round them to the nearest ten and hundred.
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Look together
Two hundreds, four tens and three ones is 243. To round it, find where it sits between the tens either side and see which one it is nearer.
Your turn
Round 42 to the nearest ten.
Put two more beads on the hundreds spike and take one bead off the tens spike. What number does the abacus show now?
Put two more beads on the hundreds spike and take one bead off the tens spike. What number does the abacus show now?
Split it another way
Split it another way
To the nearest ten and hundred
To the nearest ten and hundred
To the nearest ten and hundred
Try a little more
A whole number rounds to 370 to the nearest ten. A number ending in 5 rounds up. What is the smallest it could be, and the largest?
Try a little more
Make three-digit numbers with the cards, using each card once. How many of the numbers you can make round to 500 to the nearest hundred?
Remember
Past the middle rounds up, before the middle rounds down. A number ending in 5 rounds up.
For grown-ups
The line matters more than the rule. A child who draws the two tens either side will not need to remember which way five goes. The rounding questions after the first one have no line, so ask the child to say the two tens or hundreds either side before answering. In the two-star question the edges are the point: 365 rounds up to 370, and so does 374, but 375 does not. In the three-star question, writing all six numbers in a list before checking any of them is the method worth praising.