方程式問題~

1) Let 何伯 has y small apples,
(120-y)big apples.
(3+2)y=280
5y=280
y=56
Therefore, 何伯has 56small apples and (120-56)=64big apples.
2)Let the smallest number be y,
the second number be y+1,
the third number be y+2.
y+y+1+y+2=72
3y+3=72
3y=69
y=23
Therefore, the smallest number is 23, the second number is24 and the greatest number iss25
3)Let the present age of the son be y,
the present age of the father be 3y.
2(y+20)=3y+20
2y+40=3y+20
y=20
Therefore, the present age of the son is 20 and the present age of the father is 60.
4)Let the original amount of water in bucket A be yL,
the original amount of water in bucket B be (18-y)L.
2(y-3)=18-y
2y-6=18-y
3y=24
y=8
Therefore, the original amount of water in bucket A is 8L and the original amount of water in bucket B is 10L.
5)Let y be 甲,
(20-y) be 乙
y=2/3(20-y)
3y=40-2y
5y=40
y=8
Therefore, 甲is y and 乙is 12.


Hope I can help you!

2006-11-01 19:31:32 補充：
I am so sorry that I can't provide you the chinese translation, hope you will understand!

GOOD!!! 加油!!!

1.)何伯有蘋果120個,大的每個賣3元,小的每個賣2元,共得款280元,他共有大小蘋果各幾個?
設大蘋果是a個; 小蘋果是b個
a + b = 120
Thus, b = 120 - a
3a + 2b = 280 ……(i)
Put b = 120 - a into (i), we get
3a + 2(120 - a) = 280
3a = 240 - 2a = 280
a = 280 - 240
a = 40
Therefore,
b = 120 - a = 120 - 40 = 80

Ans. 何伯有大蘋果40個; 小蘋果80個.


2.)3個連續數之和是72,這三個數各是多少?
設3個連續數是 a, a+1, a+2
(a) + (a + 1) + (a + 2) = 72
3a + 3 = 72
3a = 72 - 3 = 69
a = 23
Therefore,
a + 1 = 23 + 1 = 24
a + 2 = 23 + 2 = 25

Ans. 3個連續數是 23, 24, and 25.

3.)父現年是子年的3倍,20年後父年是子年的2倍,父子現年各是幾歲?
設父年是a歲
設子年是b歲
a = 3b
a + 20 = 2(20 + b) ……(i)
Put a = 3b into (i), we get
3b + 20 = 2(20 + b)
3b + 20 = 40 + 2b
3b - 2b = 40 - 20
b = 20
Therefore,
a = 3b = 3 * 20 = 60

Ans. 父現年是60歲; 子現年是20歲.

4.)甲乙兩桶共盛水18升,如果從甲桶取去水3升,則乙桶的水是甲桶的2倍,甲乙兩桶原有水各多少升?
設甲桶原有水是a升
設乙兩桶原有是b升
a + b = 18
Thus, b = 18 - a
2(a - 3) = b ……(i)
Put b = 18 - a into (i), we get
2(a - 3) = 18 - a
2a - 6 = 18 - a
2a + a = 18 + 6
3a = 24
a = 8
Therefore,
b = 18 - a = 18 - 8 = 10

Ans. 甲桶原有水8升; 乙桶原有水10升


5.)甲乙兩數之和是20,甲數是乙數的2/3,甲乙兩數各是多少?
設甲數是a
設乙數是b
a + b = 20
Thus, b = 20 - a
a = 2/3 (b) ……(i)
Put b = 20 - a into (i), we get
a = 2/3 (20 - a)
a * 3 = 2/3 (20 - a) * 3
3a = 40 - 2a
3a + 2a = 40
5a = 40
a = 8
Therefore,
b = 20 - a = 20 - 8 = 12

Ans. 甲數是8; 乙數是12.

2.) n + (n + 1) + (n + 2) = 72
n + n + 1 + n + 2 = 72
3n + 3 = 72
3n = 72 - 3
3n = 69
n = 69 / 3
n = 23

1→23
2→24
3→25