太好了！
谢谢先!
The ratio of the number of girls to the number of boys in the swimming club was 4:5 ,After a group of boys entered the swimming club .40%of the new total number of children were girls.What was the percentage increase in the number of boys?
请帮忙解题!谢谢先!
最好能写上步骤.
the percentage increase 指的是占总数的百分比吗？
我不懂这里说的是不是占总数的百分比增加了多少。
非常感谢!
回复 静雯 的帖子
jug x and y contain different amounts of water at first.50% of the water in jug x was poured into jug y.then 40% of the water in jug y was poured into jug x.the final ratio of the amount of water in jug x to the amount of water in jug y was 7:6
a)what was the ratio of the amount of water in jug x to the amount of water in jug y at first?
b)if there were 10 litres of water in jug x at first,how much water was there in jug x at the end?
回复 静雯 的帖子
alina and adeline had some stickers in the ratio 3:5.when alina bought 42 more stickers and adeline bought 7 more stickers,the ratiobecame 6:7.find the niumber of stickers alina had at first.
回复 痛过的人 的帖子
Solution: (Using working backwards)
a) After the second pouring, the final ratio = 7 : 6
(The second pouring, 40% of the water in jug y was poured into jug x.
The ratio of the amount of water poured out to the amount of water left in jug y = 40% : 60% = 4 : 6.
That means 4 units water poured into jug x, so)
After the first pouring, the ratio of the amount of water in jug x to that of y =(7-4):6+4)=3:10
(The first pouring, 50% of the water in jug x was poured into jug y. There were 3 units (50%) water left in jug x. That means the original water in jug x is (3+3) units.
The original water in jug y = (10-3) units.)
The original water in jug x : the original water in jug y = (3+3) : (10-3) = 6: 7.
The ratio of the amount of water in jug x to the amount of water in jug y at first is 6:7.
b) 6 units = 10 litres ==> 1 units = 10/6=5/3 litres ==> 7 units = 5/3*7=35/3 litres.
There was 35/3 litres water in jug x at the end.
Note: It’s a good habit to check your answer.
回复 痛过的人 的帖子
When you ask your question next time, please let me know whether the problem comes from secondary book or primary book. Because we use different methods at different period. Thanks.
回复 痛过的人 的帖子
If it is a primary problem, you can do like the following:
Solution:
(The following is a table)
Alina Adeline
before change: 3 : 5 = 6 : 10 ( 6 units : 10 units)
their change: +42 +7
after change: 6 : 7 = 6 UNITS : 7 UNITS
(According to the above table, you can get: )
6 units + 42 = 6 UNITS ==> 1 unit +7 = 1 UINT (From Alina’s changed)
==> 7 UINTS = 7 units +49
10 units +7 = 7 units +49 ==> 3 units = 42 ==> 1 unit =14
6 units = 14 * 6 =84
Alina had 84 stickers at first.
回复 frekiwang 的帖子
The key to find the solution of the question is the total amount of the marbles they had unchanged.
Sorry. Could you check your data in your problem? Or scan your problem?
回复 frekiwang 的帖子
Well done!
Your working is very neat!
回复 frekiwang 的帖子
Could you correct your type error here or type your problem again?
Thanks.
回复 静雯 的帖子
Thank you very much..
建议大家在提出问题时注明题目的年级，以便别人参考。谢谢！
回复 frekiwang 的帖子
You’ve corrected your problem.
Thanks.
我女儿的数学问题，第一道：
Three boys,Aron,ben and charlie shared the cost of a birthday present for their father on his birthday.
The ratio of Aron’s share to the total of Ben’s and Charlie’s share was 1:3.
The ratio of Ben’s share to the total of Aron’s and Charlie’s shares was 1:5
Charlie paid $50 more than Ben. Fine the cost of the present .
第二道：
Susanne spent $42 on an equal number of drinks and chicken wings. Four drinks cost as much as 3 chicken wings.
Five drinks cost $2.80 more than 2 chicken wings.
How many chicken wings did she buy ?
请帮忙解答，谢谢先！.
2=15
42除以2.8 等于15。。。
画图可以看出来一个鸡翅和一个饮料加起来的价钱是2.8 。。。
谢谢娘娘！:hug:
Xavier,Yati and Zul each had a certain number of stickers.At first,Yati had 200 stamps more than Xavier and Zul had 3/4 the number of stamps Y at had.After Yati gave away 1/8 of her stamps to Xavier,she had 60 fewer stamps than Xavier.What was the ratio of number of stamps Xavier had to number of stamps Yati had to number of stamps Zul had at first?Give your answer in the simplest form.
我的解题如下：
200+60=260
260除以1/8=2080
4u=2080
1u=520
3u=1560
2080-200=1880
1880：2080：1560
=47：52：39
回复 山谷无回声 的帖子
在中国木有学过模型的啊..只会代数
呵呵，我女儿下楼买饭去了。
在中国的小学好象学的是画大括号那种方法吧？这边是画方框，估计大同小异。现在中国孩子学得越来越深了，代数，方程，什么勾股定理八成都要在小学基本上都得掌握了。
回复 山谷无回声 的帖子
我支持你的观点。
数学，在小学阶段，是思维方法的训练。
如果把代数加上了就把孩子的脑袋搞僵化了。
当然，我也不能免俗。孩子到小六时，如果不能很好地掌握模型，就学点代数吧，有利于冲高分。
所以，我认为：如果你是家长，不要过早给孩子学代数。如果你是孩子会代数不是你的错。
我们是在国内的时候老师完全已经教过了，呵呵，我觉得数学这个东西自己教还真有些困难，如果家长本身就是数学老师的话那单说，我是不主张自己教的。数学这东西真不能勉强，完全是思维的东西，定论不了孩子的智商问题。我女儿是超级喜欢数学，爱做题，爱研究，我是见数就晕，已经直接还给老师啦，哈哈。
恩，不错。不过我的观点是，要取决于孩子，如果孩子有能力就继续往前赶，不要停留，如果校内的还学不明白，就一定要打好基础，不可操之过急。
楼上是我女解的题，我用的是代数如下：
1）3X+7Y=$10
2) 4X+7Y=Z+$0.4
3) 3X+8Y=Z – $0.6
2)-3)
X-Y=$1
X=Y+$1
3(Y+$1)+7Y=$10
Y=$0.7
X=$1+$0.7=$1.7
3X$1.7+8X$0.7+$0.6=$11.3
多谢解题！
你好，请教一道小五的数学题，实在的伤脑筋，请高手帮助。
Alvin and Ken earned $6425 altogether .1/5 of Alvin’s monthly salary was $75 more than 1/6 of Ken’s monthly salary.How much money did Alvin earn each month?