數學(列式)方程式 - Ans.fyi 參考答案

數學(列式)方程式

miu hing

2008-02-02 3:17 am

1.兒子的年齡是媽媽的3/11,兒子現年9歲,問媽媽現年是多少歲?
2.兄弟三人,已知大哥20歲,二弟和三弟的年齡之和是哥哥的3/4,而二弟和三弟相差三年,問二弟的年齡?
3.啓業16年後的年齡是他12年前年齡的2倍,求他現在的年齡?
4.俊希和兒子的年齡之和是51,3年前,他的年齡是兒子的8倍,求他兒子現在的年齡?
5.成業和兒子的年齡相差32歲.6年後.他們的年齡之和是50,求他的兒子現在的年齡?
6.志強今年x歲,他的年齡是兒子的2倍多一歲,亦是女兒的3倍多兩歲,若他們三人年齡之和是(98-x)歲,求他們各人的年齡
7.陳先生比陳太太年長4歲,三年後,他們歲數之和是70,求陳先生現年歲數

回答 (2)

[匿名]

2008-02-02 5:28 am

✔ 最佳答案

英文答, 唔好意思囉......

1. Let the age of the mother be X
3/11 X = 9
X = 9 ÷ 3/11
= 9 * 11/3
= 33

2. Let the age of the second brother be X
X + X - 3 = 20 * 3/4
2X = 15 + 3
X = 18 ÷ 2
= 9

3. Let his present age be X
X + 16 = 2 * (X + 16 - 12)
X + 16 = 2 * (X + 4)
X + 16 = 2X + 8
16 - 8 = 2X - X
X = 8

4. Let the present age of the son be X
8 * (X - 3) + 3 + X = 51
8 * (X - 3) + X = 51 - 3
8X - 24 + X = 48
8X + X = 48 + 24
9X ÷ 9 = 72 ÷ 9
X = 8

5. Let the present age of the son be X
(X + 6) + (X + 32 + 6) = 50
X + 6 + X + 32 + 6 = 50
X + X = 50 - 6 - 32 - 6
2X ÷ 2 = 6 ÷ 2
X = 3

6. X + (X - 1)/2 + (X - 2)/3 = 98 - X
(X - 1)/2 + (X - 2)/3 = 98 - X - X
6 * (X - 1)/2 + 6 * (X - 2)/3= 6 (98 - 2X)
3 * (X - 1) + 2 * (X - 2) = 588 - 12X
3X - 3 + 2X - 4 = 588 - 12X
3X + 2X + 12X = 588 + 3 + 4
17X ÷ 17 = 595 ÷ 17
X = 35
Therefore,
father's age = X
= 35
son's age = (X - 1)/2
= (35 - 1)/2
= 17
daughter's age = (X - 2)/3
= (35 - 2)/3
= 11

7. Let the age of Mr Chan be X
(X + 3) + (X - 4 + 3) = 70
X + 3 + X - 4 + 3 = 70
X + X = 70 - 3 + 4 - 3
2X ÷ 2 = 68 ÷ 2
X = 34

希望幫到你 =]

參考: 自己, 學過 -w-

👍 0 👎 0

Yiu Kwong

2008-02-02 10:40 am

3.答案是40歲

👍 0 👎 0