4條百分率+方程式既數學題唔識做

1)40題就係成份測驗的80%
設數學測驗有a題:
0.8a=40
a=50
所以這次測驗有50題.
2)同上一題一樣,設這箱水果共有a個:
25%+10%=28
0.35a=28
a=80
所以這箱水果有80個.
3)設甲班有a人:
0.8a+a=81
1.8a=81
a=45
甲班有45人,所以乙班就有(81-45)=36人
4)設這筆錢原有a元:
1-(24%+28%)=48%
0.48a=96
a=200
所以這筆錢原有200元.

本人唔多喜歡用方程計,我d同學用方程計果陣,我都就咁計到so希望幫到你
1) 40/(100%-20%)
=40/80%
=50
設題數係x。
(100%-20%)x=40
2)28/(25%+10%)
=28/35%
=80
設有水果x個。
(25%+10%)x=28
3)81/(1+80%)
=81/1.8
=45
設乙班有x人。
x+80%x=81
180%x=81
4)96/(100%-24%-28%)
=96/48%
=200
設有x元。
(100%-24%-28%)x=96

人地可能打錯咋

1) ( 1- 20%)a = 40.

2) (25%+10%)a=28

3) (1=80%)a=81

4) (1-24%-28%)a=96

1.設小晴答對了x條
40除80%=x
40x100/80=x
x=50
2.設這箱水果共有x個
x乘25%+10%x=28
35%x=25
x=28除35%
x=80
3.設乙班有x人
80%x+x=81
1.8x=81
81除1.8=x
x=45
4.設這筆錢原有x元
x-(24%x+28%x)=96
x-52%x=96
48%x=96
x=96乘100/48
x=200

2007-12-26 17:49:30 補充：
見到你個補充,,,答埋你啦0.8a+a即係0.8個a加1個a咁咪係1.8個a囉a=1a 只係個1無寫出黎

1)The percentage of doing the right one is 80% (0.8), so the percentage of doing the wrong one is 20% (0.2).
Let x be the questions 小晴 did wrong.
Using ratio,
40/0.8= x/0.2
x=10
Therefore, did 10 question wrongly.
She did 10 wrong and 40 right, so the total question is 50.

2) Let x be the total number of fruit.
Using ratio,
28/0.35=x/1
Therefor, the total number of fruit is 80.

3) Let x be the number of people in
Then the number of people in will be 0.8x.
x+0.8x=81
x=45
So there are 45 people in 乙班.
The number of people in 甲班is= 45x0.8
=36
4)C has 48% of the money.
Let the total amount of money be x.
x/1=96/0.48
x=200
Therefore, 這筆錢原有 $200.

Hope this can help you.

1)數學測驗,小晴做錯了20%,做對了40題,這次測驗有多少題?
X ÷ ( 1- 20%) = 40

2)一箱水果,梨佔25%,桃佔10%,已知梨與桃共28個,這箱水果共有多少個?
(25%+10%) x X =28

3)甲,乙兩班共有81人,甲班是乙班的80%,乙班有多少人?
80% x X =81+ X

4)分一筆錢給A,B,C三人,A佔24%,B佔28%,C得96元,這筆錢原有多少錢?
X ÷ (1 - 24%-28%) = 96