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Number sense : A persons ability to use and understand numbers:-
v Knowing their relative valuesv Use them to make judgementsv Usetheminflexiblewayswhenadding,subtracting,
multiplying or dividingv Developusefulstrategieswhencountingmeasuring
or estimating
Zero
Zeroisthefirstnumberinthecountinganditiswrittenas 0. The number zero represents having no value. This canbeunderstandbyfollowingexample:
1.Suppose there are 5 birds sitting on the branch of thetree.
2.Outof5birds,2flyaway,sonow 3 birds are sitting on the branchofthetree.
3.The remaining birds also flyaway and now there are zero birdsonthebranch.
Numbers from 0 to 9 are called one digit numbers.Numbersfrom10to99arecalledtwodigitnumbers.
Historical Preview
vZero is the only number which cannot berepresented in Roman.
vZero was discovered byan Indian mathematiciannamed Aryabhatta.
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Concept Notes: Number Sense
Class-1: Mathematics
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Number l i Ne
Arrangmentofnumbersfromlefttorightinalineinincreasingorderiscallednumberline.Forexamplenumbersfrom0to10areshowninthenumberlineasfollowing.
01 2 3 4 5 6 7 8 9 10
Number line is useful in addition and subtraction and also tells the relation between thenumbers.Wewilllearnaboutnumberlineinhigherclasses.
p lace va lue of a Number
In any two digit number first numberfromrightiscalledonesandsecondnumberfromrightiscalledtens.Forexample:
eg. first number from right
Tens Ones
3 5
second number from right
→ 35 has 5 ones and 3 tens
bu i ld iNg Numbers
Building numbers from 11 to 20: Addition method is used for building of numbers for example.Whenweadd1to10thenitwillform11.Similarly,2isaddedin10togetnumber12.
Tens Ones1 1
Tens Ones1 2
Tens Ones2 0
Tens Ones1 9
Eleven
Twelve
Nineteen
Twenty
11
19
20
10 1
2
12
10
910
10 10Building Numbers From 21 to 50:Now,letustakesomeexamplestobuildnumbersfrom21to 50.When we add 1 to 20 then it will form 21.LetusunderstandwithanexampleHere = 10
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10 10 1
10 10 10
10 10 5
10 10 10 9
10 10 10 10 8
10 10 10 10 10
Twenty one
Twenty five
Thirty
Thirty Nine
Fourty Eight
Fifty
211
Tens Ones
25
30
39
48
50
5
0
9
8
0
2
2
3
3
4
5
before , a f t er aNd be tweeN
Onemorethananumbercomesafterit.Onelessthananumbercomesbeforeit.Forexample:
17 is before 18 18 is between 17 & 19
19 is after 18
compar iNg Numbers
Howwillyoucomparetwonumbers?Greaterthan(>),lessthan(<)orequalto(=)signsareusedtocomparenumbers.For example:
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Here 3 is less than 7.
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8 is more than 6.
order iNg Numbers
Numbers, when arranged from the smallest to the largest are said to be inascending or increasing order.Forexample:
Numbers canbearrangedinascendingorincreasingnumberasfollowing.
from the lowest step to the highest step
9
15
25
Numbers when arranged from the largest to the smallest are said to be in descending or decreasing order.Example:
from the highest step to the lowest step
9
15
25
backward couN t iNg
Inbackwardcountingthenumbersarewritteninreverseorder.For example
1. 50 49 48 47 46 45 44 43 42 4140 39 38 37 36 35 34 33 32 3130 29 28
2. 10 9 8 7 6 5 4 3 2 1
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s k i p couN t iNg
Inskipcounting,valueofthenumbersincreaseuniformlyForexample:(a) Skipcountingof2canbewrittenas— 2, 4, 6, 8, 10...(b) Skipcountingof3canbewrittenas— 3, 6, 9, 12, 15...
