A man is 42 years old and his son is 4 now. In how many years later will the father be as 3 times as old as his son?
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Form 1 Maths(最佳解答者have 40分)
2007-01-07 11:14 pm
回答 (10)
2007-01-09 3:07 am
✔ 最佳答案
A man is 42 years old and his son is 4 now. In how many years later will the father be as 3 times as old as his son?Solution 1:
Let x be the years after the father's age will be 3 times as old as his son.
3(4+x)=42+x
12+3x=42+x
3x-x=42-12
2x=30
x=15
So, 15 years later, the father's age will be as 3 times as old as his son.
Solution 2:
Let x be the years after the father's age be 3 times as old as his son.
x+4=(42+x)/3
x+4=14+x/3
x-x/3=14-4
2x/3=10
2x=30
x=15
So, 15 years later, the father's age will be 3 times as old as his son.
參考: my own knowledge
2007-01-08 9:44 pm
A man is 42 years old and his son is 4 now. In how many years later will the father be as 3 times as old as his son?
Let x be the time of the father being as 3 times as old as his son
42+x=3(4+x)
42+x=12+3x
42-12=3x-x
2x=30
x=15
In 15 years later will the father be as 3 times as old as his son
Let x be the time of the father being as 3 times as old as his son
42+x=3(4+x)
42+x=12+3x
42-12=3x-x
2x=30
x=15
In 15 years later will the father be as 3 times as old as his son
參考: 數學能手Me
2007-01-08 12:18 am
Answer:
Let x be the years the father will be 3 times as old as his son :
42 + x = 3 (4+x)
42 + x = 12 + 3x
3x + x = 42 - 12
2x = 30
x = 15
There the father will be 3 times as old as his son in 15 years.
Let x be the years the father will be 3 times as old as his son :
42 + x = 3 (4+x)
42 + x = 12 + 3x
3x + x = 42 - 12
2x = 30
x = 15
There the father will be 3 times as old as his son in 15 years.
2007-01-07 11:41 pm
42 + x/3 = 4 + x
42 + x = 3(4+x)
42+ x = 12 + 3x
42 -12 = 3x - x
30 = 2x
15 = x
x = 15
42 + x = 3(4+x)
42+ x = 12 + 3x
42 -12 = 3x - x
30 = 2x
15 = x
x = 15
參考: me
2007-01-07 11:30 pm
Let x be the year after the father's age will be as 3 times as old as his son .
42+x / 4+x =3
42+x =12+3x
42-12= 3x-x
30 = 2x
x = 15
∴ The father's age will be as 3 times as old as his son after 15 years.
42+x / 4+x =3
42+x =12+3x
42-12= 3x-x
30 = 2x
x = 15
∴ The father's age will be as 3 times as old as his son after 15 years.
2007-01-07 11:26 pm
Let x be the year later:
42+x = (4+x) X3
42-12+x = 3x
30= 2x
x = 15
42+x = (4+x) X3
42-12+x = 3x
30= 2x
x = 15
2007-01-07 11:23 pm
Shall we let x years later, the age of the father is 3 times as the son's.
42+x = 3(4+x)
42+x = 12+3X
2x = 30
x =15
Therefore, 15 years later, the age of the father is 3 times as the son's.
And by the time, the father will be 57 and the son will be 19.
42+x = 3(4+x)
42+x = 12+3X
2x = 30
x =15
Therefore, 15 years later, the age of the father is 3 times as the son's.
And by the time, the father will be 57 and the son will be 19.
2007-01-07 11:23 pm
Let x be the years the father will be 3 times as old as his son :
42 + x = 3 (4+x)
42 + x = 12 + 3x
3x + x = 42 - 12
2x = 30
x = 15
There the father will be 3 times as old as his son in 15 years.
2007-01-07 15:23:34 補充：
oops, it should be THEREFORE.
2007-01-07 15:25:22 補充：
o and, it shold be 3x-x. sorry
42 + x = 3 (4+x)
42 + x = 12 + 3x
3x + x = 42 - 12
2x = 30
x = 15
There the father will be 3 times as old as his son in 15 years.
2007-01-07 15:23:34 補充：
oops, it should be THEREFORE.
2007-01-07 15:25:22 補充：
o and, it shold be 3x-x. sorry
參考: myself
2007-01-07 11:22 pm
Let x years later will that the father be as 3 times as old as his son,
42 + x/3 = 4 + x
42 + x = 3(4+x)
42+ x = 12 + 3x
42 -12 = 3x - x
30 = 2x
15 = x
x = 15
hence,the required answer is 15 years
hope its help:)
42 + x/3 = 4 + x
42 + x = 3(4+x)
42+ x = 12 + 3x
42 -12 = 3x - x
30 = 2x
15 = x
x = 15
hence,the required answer is 15 years
hope its help:)
參考: by eason mensa
2007-01-07 11:20 pm
Let x years later will the father be as 3 times as old as his son
42 + x / 3 = 4 + x
42 + x = 3(4+x)
42+ x = 12 +3x
42-12 = 3x - x
30 = 2X
15 = x
x = 15
15 years later will the father be as 3 times as old as his son
42 + x / 3 = 4 + x
42 + x = 3(4+x)
42+ x = 12 +3x
42-12 = 3x - x
30 = 2X
15 = x
x = 15
15 years later will the father be as 3 times as old as his son
參考: 自己
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