1.(a) What is the area of the semi-circle of radius 14 cm?
(b) If the area of a circle is 25cm^2, what is its radius?
2. The volume of a cylider of base radius 7 cm is 1 540cm^3. Find
(a) its height,
(b)its total surface area.
*(Take pi=7/22)
急!!!f.2英文數呀~~~
2008-04-12 5:19 am
回答 (2)
2008-04-12 8:40 am
Let pi be 22/7 as I can't type pi here
1a
22/7 X 14^2 / 2
=308
b
Let radius = r
22/7 X r^2 = 25
r= 2.82038...
2a
Let height=h
22/7 X 7^2 X h = 1540
h=10
b
total surface area = base X2 + curved area
=pi X r^2 X2 + 2 X 22/7 X r X h
=22/7 X 7^2 X2 + 2 X 22/7 X 7 X 10
= 308+220
=528
add back the units and check it once again=]
btw pi=22/7
2008-04-12 00:42:47 補充：
2b I left the X2
the curved are should = 440
therefore the total surface area = 748
1a
22/7 X 14^2 / 2
=308
b
Let radius = r
22/7 X r^2 = 25
r= 2.82038...
2a
Let height=h
22/7 X 7^2 X h = 1540
h=10
b
total surface area = base X2 + curved area
=pi X r^2 X2 + 2 X 22/7 X r X h
=22/7 X 7^2 X2 + 2 X 22/7 X 7 X 10
= 308+220
=528
add back the units and check it once again=]
btw pi=22/7
2008-04-12 00:42:47 補充：
2b I left the X2
the curved are should = 440
therefore the total surface area = 748
2008-04-12 5:51 am
Answers:
1.(a)~area=(22/7)x(14)^2x(1/2)=308cm^2
(b)~radius=2.82cm(corr. to 3 sign.fig.)
2.(a)~height=(1540)/(49x22/7)=10cm
(b)~total surface area=(10x2x7x22/7)+2x(49x22/7)
=440+308
=748cm^2
(P.S.~你個pi錯左...應該係22/7,唔係7/22......)
2008-04-11 21:54:50 補充：
下次計數要careful啲,唔好寫錯個pi啦...
1.(a)~area=(22/7)x(14)^2x(1/2)=308cm^2
(b)~radius=2.82cm(corr. to 3 sign.fig.)
2.(a)~height=(1540)/(49x22/7)=10cm
(b)~total surface area=(10x2x7x22/7)+2x(49x22/7)
=440+308
=748cm^2
(P.S.~你個pi錯左...應該係22/7,唔係7/22......)
2008-04-11 21:54:50 補充：
下次計數要careful啲,唔好寫錯個pi啦...
收錄日期: 2021-04-13 15:25:22
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