又一題 [複製鏈接]

Peter is 12 years old and his grandfather is 63 years old now.
a)After how many years time will Peter's age be 4分1 of his grandfather's age?
b)How many years ago was grandfather's age 18 time Peter's?



教教我!!

a.)

Let x be the years time that Peter's age will be 1/4 of his grandfather's age

12+x=(63+x)/4

(12+x)x4=(63+x)/4x4

48+4x=63+x

48=63+x-4x

48-63=x-4x

-15=-3x

-15/-3=x

5=x

x=5

"After 5 years , Peter's age will be 4分1 of his grandfather's age.

b.)

Let x be the year time that grandfather's age 18 time Peter's

63-x=(12-x)x18

63-x=216-18x

63-216=-18x+x

-153=-17x

x=-153/-17

x=9

"9 years ago , grandfather's age was 18 times of Peter's age

thx~答案岩左
但點解@o@

引用第2樓影於2006-09-27 20:47發表的“”:
thx~答案岩左
但點解@o@

Let x be the years time that Peter's age will be 1/4 of his grandfather's age

(12+x)=(63+x)/4(peter而家個age再加個年數就等於grandfather個age加年數，peter就係1/4 age of grandfather)

(12+x)x4=(63+x)/4x4

48+4x=63+x

48=63+x-4x

48-63=x-4x

-15=-3x

-15/-3=x

5=x

x=5

"After 5 years , Peter's age will be 4分1 of his grandfather's age.

b.)

Let x be the year time that grandfather's age 18 time Peter's

63-x=(12-x)x18(grandfather係63歲，x年前係peter既18倍，)

63-x=216-18x

63-216=-18x+x

-153=-17x

x=-153/-17

x=9

"9 years ago , grandfather's age was 18 times of Peter's age

成堆英文，唔識睇
計年齡唔係好難計掛

我數學差

係咪一定要用英文設= =

第一題


設x年後peter的年齡為peter's grandfather4份一倍
4(12+x)=63+x
48+4x   =63+x
3x       =15
x       =5

答:........................



設y年前peter's grandfather為peter的18倍

18(12-y)=63-y
216-18y=63-y
153     =17y
y       =9


答:........................

交左功課lu= =唔知幾多分

引用第7樓影於2006-09-28 18:47發表的“”:
交左功課lu= =唔知幾多分

[題外]你用緊邊本maths書,我用緊人教[/題外]

人教?乜黎..我本數學冇一版係中文~