3. Barry is counting how many marbles he has altogether. He has 7 different types of marbles, each in their own bag.


a) Estimate how many marbles Barry has altogether by rounding the number in each bag to the nearest ten.


b) Check how close your answer was by adding the amount of marbles in each bag.


4. Have a go at rounding these numbers to the nearest ten. (Hint: no matter how big the number is, when rounding to the nearest ten you only need to look at the units.)


a) 788 f) 3461


b) 543 g) 1708


c) 244 h) 2516


d) 607 i) 15355 e) 986 j) 71348


5. Rounding Riddles – what number am I? a) I am a multiple of 9 and am 40 when rounded to the nearest ten. b) I am the number of months in the year rounded to the nearest ten. c) I am the number of days in the year rounded to the nearest ten. d) I am the number of holes on a golf course rounded to the nearest ten. e) Invent 3 of your own Rounding Riddles.


Rounding to the Nearest Hundred


As we learned in 4th class, if you are asked to round a number to the nearest hundred, you must say the multiple of one hundred that is nearest to that number. (Multiples of one hundred are 100, 200, 300, 400, 500, 600 and so on.)


It helps to look at a number line. For example: Round 475 to the nearest hundred. 400


390 410 420 430 440 450 460 470 475


Look at where 475 is on the number line. Which multiple of one hundred is it nearer to, 400 or 500?


It is nearer to 500. Therefore, 475 rounds up to the nearest hundred, which is 500.


When rounding in hundreds, if there are less than five tens, we round down to the nearest hundred, but if there are five tens or more, we round up to the nearest hundred.


Note:  Numbers 401 to 449 round down to 400 because they are nearer to 400 than 500.  Numbers 451 to 499 round up to 500 because they are nearer to 500 than 400.  Number 450 is exactly halfway between 400 and 500. The rule in this case is to round up to 500.


Place Value 15 480 490 500 510


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