ｌａｓｔ ｍａｔｈｓ題唔該
回答 (6)
2006-12-08 1:15 am
✔ 最佳答案
50cents的金幣=N枚$2金幣=(300 - N)枚
$0.5N + $2(300 - N) = $300
0.5N + 600 - 2N = 300
600 - 1.5N = 300
1.5N = 300
N = 200
$2金幣=300 - (200)
$2金幣=100枚
所以答案係 100枚。
參考: self solve
2006-12-08 1:18 am
Let a be the no of 50 c (i.e.$0.5) and b be the no of $2 coins :
0.5a+2b=300.......................(1)
a+b=300..............................(2)
(1) x 2 : 2(0.5a+2b)=300x2
a+4b=600................(3)
(3)–(2) : (a+4b)-(a+b) = 600-300
a+4b-a-b = 300
3b = 300
b=100
∴There are 100 $2 coins
0.5a+2b=300.......................(1)
a+b=300..............................(2)
(1) x 2 : 2(0.5a+2b)=300x2
a+4b=600................(3)
(3)–(2) : (a+4b)-(a+b) = 600-300
a+4b-a-b = 300
3b = 300
b=100
∴There are 100 $2 coins
2006-12-08 1:18 am
設五毫(50c)為x, $2為y
得出兩條方程式.....
300 = x + y---------(1)
300 = 0.5x + 2y---------(2)
由(1)
y = 300 - x--------(3)
代(3)入(2)
300 = 0.5x + 2(300 - x)
x = 200
所以y = 100
$2金幣有100個
得出兩條方程式.....
300 = x + y---------(1)
300 = 0.5x + 2y---------(2)
由(1)
y = 300 - x--------(3)
代(3)入(2)
300 = 0.5x + 2(300 - x)
x = 200
所以y = 100
$2金幣有100個
2006-12-08 1:16 am
0.5N + 2 ( 300 - N ) = 300
0.5N + 600 - 2N = 300
-1.5N = -300
N = 200
Checking :
0.5( 200 ) + 2 ( 300 - 200 ) = 300
100 + 200 = 300
300 = 300
200枚是50c/金幣 , ( 300 - N ) = 100枚是 $2金幣.
0.5N + 600 - 2N = 300
-1.5N = -300
N = 200
Checking :
0.5( 200 ) + 2 ( 300 - 200 ) = 300
100 + 200 = 300
300 = 300
200枚是50c/金幣 , ( 300 - N ) = 100枚是 $2金幣.
2006-12-08 1:09 am
(0.5 x N ) + ( 2 x (300 - N)) = 300
0.5N + (600 - 2N) = 300
0.5N + 600 - 2N = 300
-1.5N + 600 = 300
-1.5N = 300 - 600
-1.5N = -300
N = 200
0.5N + (600 - 2N) = 300
0.5N + 600 - 2N = 300
-1.5N + 600 = 300
-1.5N = 300 - 600
-1.5N = -300
N = 200
參考: personal smartness (:
2006-12-08 1:08 am
0.5N+2(300-N)=300
1.5N=300
N=200
所以共有300-200=100枚$2金幣
1.5N=300
N=200
所以共有300-200=100枚$2金幣
收錄日期: 2021-04-12 19:34:47
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061207000051KK02378