中二數學問題求幫忙(10點)

1.The number of significant figures in the number of 230.00 is:
(B).3


2.Change the following fractions into decimal numbers,correct the answers to 2 significant figures.(我唔知你洗5洗寫step)
(A)4/9 = 0.444444444.... = 0.44

(B)-1/2/3 = -1.6666666677.... = -1.7


3.Estimate the value of the following expressions.( "~" refers to大約等於)
(A)139.6 ~ 140, 59.82 ~ 60
139.6+59.82 ~ 140+60 =200

(B)403.06 ~ 403, 79.12~79
403.06-79.12 ~ 403-79 = 324

(C)19.9 ~ 20, 3.17~ 3
19.9*3.17 ~ 20*3 = 60

(D)88.13 ~ 88, 11.02 ~ 11
88.13/11.02 ~ 88/11 = 8

(E)27.13 ~ 27, 3.04 ~ 3, 11.19 ~ 11
27.13*3.04-11.19 ~ 27*3-11 = 70

(F)30.16 ~ 30, 9.97 ~ 10
30.16^2-9.97^2 ~ 30^2-10^2 = 800


hope can help u: )

1. (D)5
2. (A)4/9=0.44
(B)-1/2/3=-1.7
3.(A)140+60=200
(B)400-80=320
(C)20*3=60
(D)90/10=9
(E)30*3.0-10=80
(F)30^2-10^2=800

Hope I can help you!