EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
WhyEstimate?
Whatisestimationandwhydoweestimate?
EstimationgivesacloseAPPROXIMATIONofanumber.
Weestimatewhenwe’reinahurryoraccuracyisn’tthat
important.
Therearemanymethodsofestimation!We’lllearn3
methods.
Method#1:
Whatisrounding?
Rounding
Findingoutwhich“benchmarknumber”anumberisclosest
to.Thinkofanumberline!
Whatisabenchmarknumber?
A“nicer”number;Benchmarknumbersusuallyendinazero
(tens,hundreds,thousands,etc.)
Howdoyouroundanumber?
1.) Determinewhichplacevaluepositionyou’rerounding
to(howaccuratedoyouneedtobe?).
2.) Lookatthedigittoitsright.
3.) Ifit’s5ormore,roundup.(makethedigitbigger)
4.) Ifit’slessthan5,rounddown.(leavethedigitthe
same).
5.) Alldigitstotheleftstaythesame.
6.) Alldigitstotherightbecomezeros.
What’sthedealwith5’s?
Fiveisexactlybetweentwobenchmarknumbers.
Mathematiciansagreedthatanumberexactlybetween2
benchmarknumberswillalwaysberoundedup.
Practice:
Roundtothenearestwholenumber:
1.) 4.675à5
2.) 3.192à3
3.) 6.923à7
Roundtothenearesttenth:
4.) 4.675à4.7
5.) 3.192à3.2
6.) 6.923à6.9
Roundtothenearesthundredth:
7.) 4.675à4.68
8.) 3.192à3.19
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources
EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
9.) 6.923à6.92
Method2:
Whatarecompatiblenumbers?
Compatible
Numbersthatareeasiertocomputetogether.57 ÷ 7isnot
Numbers
easytocomputementally,but56 ÷ 7iseasier.Thequotients
areclosetothesame,though!
Copytheproblemontheboard.Replaceeachnumberwitha
compatiblenumber,thenestimatethequotient.
48.9 ÷ 8.9
Compatiblenumbers:48 ÷ 8 = 6
Howdoyouchoosethebestcompatiblenumbers?
Lookfornumbersthatareclosetotheoriginalnumbers,so
yourestimateisasaccurateaspossible.Findnumbersthat
areeasytocomputementally(thinkmultiplicationfacts!)
Practice:
Usecompatiblenumberstoestimate:
1.) 42.6x3.1≈40x3=120
2.) 18.5 ÷ 6.2 ≈ 18 ÷ 6 = 3
Method3:FrontWhatisfront-endestimation?
endEstimation
Usingthewholenumberpartofanumbertogetaquick
estimate,thenadjustingforthedecimalparts
Howdoyouusefront-endestimation?(It’sa2-stepprocess!)
Ignorethedecimalpart.Computeusingthewholenumbers
only.
Then,adjustforthedecimal.Lookfordecimalsthatareclose
to0,½or1(dependinghowcloseyourestimateneedstobe).
Whatdoyoulookforwhen“adjusting”yourfront-end
amount?
Twohalvesadduptoonewhole.
Verysmalldecimalscanbeignoredsometimes.
Lookfordecimalsclosetoone.
Practice:
Usefront-endestimation:
10.)
8.52+9.25+1.26≈8+9+1=18,andanother
1fromthedecimals=19
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources
EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
11.)
11.45+8.52+1.98=11+8+1=20,and
another2fromthedecimals=22
12.)
Johnwenttothecandystoreandboughtabag
ofM&Msfor$1.88,aboxofNerdsfor$0.98,anda
containerofBubbletapefor$1.02.Abouthowmuch
didJohnspend?
13.)
1+0+1,andanother2incents≈$4
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources
EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
WhyEstimate?
Whatisestimationandwhydoweestimate?
Therearemanymethodsofestimation!We’lllearn3
methods.
Method#1:
Whatisrounding?
Rounding
Whatisabenchmarknumber?
Howdoyouroundanumber?
What’sthedealwith5’s?
Practice:
Roundtothenearestwholenumber:
1.) 4.675
2.) 3.192
3.) 6.923
Roundtothenearesttenth:
4.) 4.675
5.) 3.192
6.) 6.923
Roundtothenearesthundredth:
7.) 4.675
8.) 3.192
9.) 6.923
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources
EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
Method2:
Whatarecompatiblenumbers?
Compatible
Numbers
Copytheproblemontheboard.Replaceeachnumberwitha
compatiblenumber,thenestimatethequotient.
Howdoyouchoosethebestcompatiblenumbers?
Practice:
Usecompatiblenumberstoestimate:
10.)
42.6x3.1=
11.)
18.5 ÷ 6.2 = Method3:FrontWhatisfront-endestimation?
endEstimation
Howdoyouusefront-endestimation?(It’sa2-stepprocess!)
Whatdoyoulookforwhen“adjusting”yourfront-end
amount?
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources
EstimatingwithDecimals
Name:
Math6
Date:
Chapter1–Lesson4
Practice:
Usefront-endestimation:
12.)
8.52+9.25+1.26=
13.)
11.45+8.52+1.98=
14.)
Johnwenttothecandystoreandboughtabag
ofM&Msfor$1.88,aboxofNerdsfor$0.98,anda
containerofBubbletapefor$1.02.Abouthowmuch
didJohnspend?
Moreresourcescanbefoundonourclasswebsite:www.elliottsttims.weebly.com/resources