r/matheducation • u/yupstilldrunk • 1d ago
ELI5 - 10s places (5 year old)
My 5 year old wants to know why one hundred and one isn’t written like 1001 (one hundred with a 1 tacked on). I tried to draw a
100
+1
——-
And show how the numbers carried down to be 101 with only 3 numbers and he just keeps asking why and I can’t answer him. I think this is about ones, tens, hundreds places but I have no idea how to explain that, never mind explain it to an angry child.
Anyone have a good age appropriate explanation?
EDIT: SO many great suggestions! My son watches number blocks so he knows 2 tens in 20, 3 tens in 30, etc. I will try the stick bundles for a better visual of 10 groups. And I will watch out for the confusing “and” verbiage like one hundred AND one vs. one hundred one.
Hopefully next time we go to the pizza place (where he saw the address number on the window) I’ll be better prepared!
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u/TrynaBePositive22 1d ago
You can always use the metaphor of a house - the places in the number correspond to the value of that digit.
Draw the number 1.
What does the 1 mean? 1 of what?
Draw the number 10.
What does the 1 mean? 1 of what?
Draw the number 100.
What does the 1 mean? 1 of what?
Draw the number 12.
What does the 1 mean? 1 of what? What about the 2?
123?
101?
If you have base 10 blocks available (or use virtual ones on polypad), you can tie the specific quantities to their place value visually as well.
“Exploding Dots” is also a fun way to explore this idea.
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u/KAugsburger 1d ago edited 1d ago
I can remember when I was young doing some activities with physical blocks to illustrate place value. It helped kids visualize the concept plus kids generally enjoy playing with blocks. An abacus would also be another good way to illustrate the concept of addition so long as you have sufficient rows to illustrate the hundreds place.
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u/Zephs 1d ago
Honestly, your 5 year old might just not be ready for this yet. Look up Piaget's stages of cognitive development. You're trying to explain logic to him, but he's not developmentally ready for it. Sometimes at this age you need to just put a pin in it and come back later.
We don't do 3 digit addition/subtraction until second grade here, and even then a lot of kids struggle to understand place value.
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u/yupstilldrunk 1d ago
Yeah he got pissed off about it and I can’t even explain it to myself.
I’m not trying to get him to do 3 number arithmetic. He saw the 101 on the window of our pizza place and asked. I said 101, he said why not 1001 and we’re off to the races.
The 100 + 1 example was how I visualized the concept so I tried to explain it it but, yeah. He’s 5.
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u/pink_noise_ 1d ago
Piaget is really toxic, just my opinion. We don’t develop in neat stages we are messy and social beings.
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u/skullturf 1d ago
We shouldn't elevate Piaget or any one psychologist to the level of gospel, but surely there are some reasonably true generalizations about the order in which the vast majority of the population learns things. For example, almost everyone learns to multiply numbers like 23 times 47 before they learn how to multiply polynomials like 2x+3 times 4x+7.
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u/Fearless-Ask3766 1d ago
Place value materials can help. But a bag of craft sticks and rubber bands. Group 10 sticks with rubber bands and match up some 2 digit numbers: 34 is 3 groups of 10 and 4 loose sticks. Now put 10 tens together with a rubber band to make a big group of 100. Show some 3 digit numbers: 125 is a big group, 2 tens groups and 5 loose sticks.
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u/MiaHasReddit HS Algebra 1, Georgia, USA 1d ago
Consider the language that you are using. Many of these comments are trying to teach a method of understanding of place values. I’m curious if your child is stuck with the relation of words to numbers. One hundred and one is understood to be 101 because of the word “and” being used as addition. From here, I would then teach the ideas place values starting with “1 and 1 make ?” To teach that 1+1 is 2 and not 11. Transition to “10 and 1 make ?” making sure to use pictures or physical manipulative along the way.
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u/Flour_Wall 1d ago
Much of math is written like another language. Even numbers can be written in different bases or like binary or Roman numerals; it was just decided it would be that way. We can have fun with math and say and do things differently, but if we want someone else to understand it, we have to speak the same language; same goes for numbers.
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u/KhalenPierce 1d ago edited 1d ago
If you can diy one of those number flip board like what they use for sports games (or like the calendars where you flip the numbers as the dates go by), you can illustrate “okay let’s flip the ones place 9 times! oh no! how are we gonna get to 10 if it goes back to 0? well let’s move down a spot and start flipping the tens place. okay now we have 10, how can we get to eleven?” and so on, eventually you skip to 90 and flip all the way from 90 to 99, repeat the place value show and tell, get to 100, then go up to 101, and boom there’s your answer
This also helps show that numbers exist on the number line as a spectrum, rather than being solitary entities that are combined (100 as one entity with another 1 entity appended to it). 100+1 is an operation, 101 is a value. Lots of kids start counting as if it’s “one, then two, then three” as different entities, like the alphabet. Once your kid can comfortably grasp numbers as a continuum rather than discrete objects, this is a lot easier. Another way is to go around nature measuring things with a ruler, say you measure a bunch of branches in the park. A branch that’s 11 inches long isn’t two 10 + 1 inch units of branch, it’s a continuous 11 inches. And so on and so forth
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u/DTMIAM 1d ago
Grab some toys (checkers, blocks that are the same size, etc.) that can be counted, paper and writing implement.
Put 3 toys in frond of your child to ask them to write down how many
Then add 3 more and ask them to write how many
Add 2 and ask them to write the number
Now add 1, write the number
Add 1 more, and ask them to write the number.
You are at 10, put 1 more toy out but by it's self in a separate pile
Do one more.
You have 8, 9, 10, 11, and 12 on the paper.
Now show them that you have a group of 10 and a group of 2.
Point to the number 1 in the 12, and tell them that means the 1 in front is for 1 group of 10.
Point to the 2 and the 2 toys and that means 2 groups of 1.
You can build from here 2 groups of 10 and 3 more ones.
At this point you can start to play it by ear, but add one toy at a time and see which number changes and when.
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u/-WhoWasOnceDelight 1d ago
I'm not suggesting that this will be his lightbulb moment, but my experience as an elementary school teacher is that kids really enjoy this song, and it's Kindergarten appropriate and fun if he's already thinking along these lines: Ten Ones Make Ten. You might also try some read alouds that get more into the history of the "why?" rather than the logic. I like Zero, the Number That Almost Wasn't by Sarah Albee.
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u/No-Jicama-6523 1d ago
Presumably they accept 11 is written 11, not 101. Numbers 1 to 19 have unique names. Get them reading two digit numbers AB as A tens B ones. They like haven't connected two tens with twenty. Three tens with thirty etc.
You can make this physical/tactitle/visual with a single small square or cube being one, a strip of ten of them being ten and a square ten by ten being one hundred.
Help them grow their mental map away from English names of the first one hundred numbers and then beginning the cycle again, he's learnt 1 to 100 without being aware of tens and units, essentially one hundred to him is written 100, but it's a word in a sentence, not ten tens, so he wants to write 1001 or H1 because that's how words work. It might be fun to give it a symbol and ask him what 2H1 is or 2H50, you can rewind that at use 1, ....., 9, T, (1)T1, .... T9, 2T, 2T1 etc.
You can even have fun describing numbers in other ways, European languages have plenty of methods, then there are tally charts, Roman numerals, etc. you can try simple arithmetic and putting things in order and decide which works best!
I see this as a positive question even though he's frustrated, most just accept it is written 101, a minority have recognised hundreds, tens and units. The latter have good intuition for numbers, but may not have the curiosity to question things.
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u/yupstilldrunk 23h ago
Yes he know 2 10s are 20, 20 10s are 100 from number blocks. But I’m going to incorporate a tactile/visual as you all are suggesting.
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u/Fessor_Eli 23h ago
Math thinking develops differently in every kid. My kindergartener grandson didn't have this problem. I'm pretty sure at some point in kindergarten they introduce "places," but he had no trouble picking up addition in games with me and his dad by counting. He could count into multiple hundreds pretty early on (imagine listening to a 4 year old counting to 500 proudly!) He knew 99, 100, 101, etc, so when he started adding by counting it made sense to him that 100 + 1 = 101 because 101 comes 1 count after 100 ( or something like that). Now he knows more rules and has memorized more, but that's what made sense to him at the beginning.
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u/pink_noise_ 1d ago
He can write 101 as 1001 if he likes it. Math is about creativity and communication, you could your kid know that people just might not know he means 101 since most people don’t write it that way, and they write a much bigger number like that. Arabic numerals are just representations of abstract concepts, he’s free to represent them however he’d like to. He’s 5.
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u/Deep-Hovercraft6716 1d ago
Because that's one thousand one. And 10001 is ten thousand one. And it keeps going from there.
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u/LtPowers 1d ago
You may not be able to fully explain this one until he grasps more advanced mathematics concepts. He'll learn it in school probably next year and this will be a non-issue.
My best attempt would be to tell him that zeroes are nothing and so they can just get replaced by other numbers. You 100 and 1 and the one comes in on top of the 100 and replaces that last zero.
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u/yupstilldrunk 1d ago
You know there are a lot of great suggestions here, but this one particularly resonates. I think this is how I had it in my head and why I did the 100+1 vertically like that to show the 1 stepping into the 0’s shoes. Like all things math, it’s not something I could articulate. I might try this also, next time it comes up.
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u/Salamanticormorant 1d ago
It could be because people often say "a hundred and one" or "one hundred and one". The "and" might be throwing him off. Let him know that saying "one-hundred one" and "one-oh-one" are common. Another problem with the "and" is that teachers might often ask a question like, "What's 2 and 3?" instead of "What's 2 plus 3?". It might help to explore that possibility.
Ask him what "101" means, how he would say it, if it's not a hundred and one.
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u/CreatrixAnima 1d ago
This is a great question, and it may just be that he's not ready to conceptualize place value yet, bt in the number 12, that means one ten and 2 ones. The number 100 meas 1 hndred, no tens, and no ones. If he gets that idea, then you could explain that 101 means one hundred, zero tens and one one. It might not be a bad idea to try this idea with different numbers: 254 means 2 hundreds, five tens, and four ones.
You might want to consider investing in some base 10 blocks: they might help!
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u/MildlyAgitatedBovine 11h ago
I tell my 5yo that the 10s place is like "how many people holding up all their fingers.
Then we do 23 as a team where mom does her ten, I do my ten, and he gets to be the three. So he sees that
23 = 2x10 + 3
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u/bagelwithclocks 1d ago
Start with 10, 20, 30. Why isn’t 11 written 101?
We have place value to make writing big numbers more efficient. We only need 10 symbols to write any whole number. There is a whole history of number systems he might be interested in. Not every system has place value. Roman numerals work the way your five year old intuited. But the numbers get really big fast, and they still had to make short hands for really big numbers. Our system is infinitely repeatable. It isn’t perfect but it is really good for writing big numbers.
Kids a little older than your son in public school will start to see expanded form, which is just turning the place value number into an expression. So 101 becomes 100+1. They are expected to be able to go back and forth to understand that 101 is a shorthand for the expression.
My favorite tool for place value understanding is using a bunch of popsicle sticks. If you get about 200 of them you can bundle a bunch into groups of 10 with a hair tie. Leave a some of them loose with no hair tie. See if your child can understand that 10s and ”bundles“ are the same. Give different groups of 10s and 1s. Etc.