A box contains two kinds of coins:$5and $2.The ratio of the number of $5 coins to the number of $2 coins is 4:5.If the total value of the coins is $90, then the total number of coins in the box is.......
A)9
B)18
C)27
D)36
maths mc
2007-04-26 8:52 pm
回答 (5)
2007-04-26 8:58 pm
✔ 最佳答案
Let C be the total number of coins5*(4C/9)+2*(5C/9)=90
20C/9 + 10C/9 =90
30C/9 =90
30C =810
C =27
Therefore,the number of coins in the box is 27
Hope that it helps :)
2007-04-26 13:00:58 補充：
The right answer is C~I forgot to type just now...sorry
2007-04-26 9:06 pm
$5 : $ 2 = 4 x : 5 x
$ 5 ( 4x ) + $ 2 ( 5x ) = $ 90
20 x + 10 x = 90
30 x = 90
x = 3
so $ 5 = 4 x 3 = 12
$ 2 = 5 x 3 = 15
12 + 15 = 27
the ans. is c
$ 5 ( 4x ) + $ 2 ( 5x ) = $ 90
20 x + 10 x = 90
30 x = 90
x = 3
so $ 5 = 4 x 3 = 12
$ 2 = 5 x 3 = 15
12 + 15 = 27
the ans. is c
參考: me
2007-04-26 9:04 pm
C
let the no. of $5coin be X
the no. of $2coin be5/4X
5(X)+2(5/4X)=90
15X=180
X=12
thus,the total no. of the coins is 12+(5/4)(12)=27
let the no. of $5coin be X
the no. of $2coin be5/4X
5(X)+2(5/4X)=90
15X=180
X=12
thus,the total no. of the coins is 12+(5/4)(12)=27
2007-04-26 9:02 pm
設有x個$5硬幣,有y個$2硬幣
5x+2y=90 - (1)
x/y=4/5 - (2)
由(2)
5x=4y - (3)
代(3)進(1)
6y=90
y=15
代y=15入(3)
5x=60
x=12
所以盒入面有的硬幣
=x+y
=27
答案:C
5x+2y=90 - (1)
x/y=4/5 - (2)
由(2)
5x=4y - (3)
代(3)進(1)
6y=90
y=15
代y=15入(3)
5x=60
x=12
所以盒入面有的硬幣
=x+y
=27
答案:C
2007-04-26 8:59 pm
Let x & y be the number of $5 & $2 coins respectively.
(1) x:y=4:5 => x = 4y / 5
(2) 5x+2y=90
5x + 2y = 90
5 (4y / 5) + 2y = 90
4y + 2y = 90
6y = 90
y = 15
x = 4y / 5
= 4 (15) / 5
= 12
Total number of coins = x + y
= 12 + 15
= 27
Therefore, ans = C.
(1) x:y=4:5 => x = 4y / 5
(2) 5x+2y=90
5x + 2y = 90
5 (4y / 5) + 2y = 90
4y + 2y = 90
6y = 90
y = 15
x = 4y / 5
= 4 (15) / 5
= 12
Total number of coins = x + y
= 12 + 15
= 27
Therefore, ans = C.
參考: me
收錄日期: 2021-04-13 00:25:40
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