英文數學文字題(方程)(4題)(20分)

2008-02-06 8:31 am

(用方程)

1.In a supermarket, the price of an apple is $2.5, and a orange is $3. Alan got $2 left after buying some apples. However, her would need $2 more if he wanted to buy the same number of oranges. Find the number of apples he bought.

2. Jane bought x tarts,she ate 1/4(四分之一)of them,then her brother and sister ate 7 tarts and 2 tarts were left.Find the value of x.

另外2題之後打~

更新1:

3.1/4(四分之一)of a mother's age is 1 year less than 1/2(二分一)of her daughter's age. If the sum of their ages is 62, fing their ages. 4.The sum of 2 times a number and 6 is divided by3. If the result is12,find the number.

更新2:

第3題忽略 #@39 其實應該係 daughter一個posofivess s(daughter,s)

回答 (2)

用戶3988

2008-02-06 9:01 am

✔ 最佳答案

1) Let x be the number of apples Alan bought (ie the number of oranges he bought also)
Let y be the total money Alan originally has
{y - 2.5x = 2 -------(1) [總金錢 - X咁多個值$2.5既apple = 淨番 2蚊]
{y+2 - 3x = 0 ---------(2) [ 總金錢 + $2 - X咁多個值$3既orange = 0 ]
From (1) y = 2 + 2.5x
Sub y = 2 + 2.5x into (2)
2 + 2.5x + 2 - 3x = 0
0.5x=4
x=8
Thus the number of apples he bought is 8.

2)
[X x 1/4] - 7= 2 { 1開始 Jane 食左 X中既1/4.. 之後佢brother同sister食左7個(所以-)}
X x 1/4 = 9
X = 36
The value of X is 36.

3) M = mother's age, D= Daughter's age
{M x 1/4 + 1 = D x 1/2 ------(1) [ "A is 1 year less than B" 即係 "B比A多1年" , 所以 A 要+1年先= B]
{M + D = 62 ---------- (2)
From (2)
M = 62 - D ------(3)
Sub (3) into (1)
[(62-D)/4] + 1 = D/2
4 times the equation
62-D + 4 = 2D
66=3D
D = 22
When D = 22, M = 40.

4) (2N + 6)/3 = 12
2N + 6 = 36
N=15

2008-02-06 16:43:24 補充：
oops sorry..#2 果題我錯了..

參考: I hope the answers i writen are all correct.

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[匿名]

2008-02-06 9:11 am

1. let the number of apples he bought be X
2.5X+2+2=3X
0.5X =4
X=8

2. (1-1/4)*X-7=2
3/4X=9
X=12

3. let X and Y be the ages of the mother and her daugter repectively
a. X+Y=62
b. 1/4X+1=1/2Y
multiply equation (b) by 4, we get
X+4=2Y
equation (a) - equation (b), we get
Y-4=62-2Y
3Y =66
Y=22
if Y=22,X=62-22=40

4. let the number be X
(2X+6) / 3 = 12
2x= 30
X= 15

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