唔該幫幫忙!!!勁急~~~數學題 (10分)

7分之a+6=5分之a

a/7+ 6 = a/5
a/7 + 42/7 = a/5
(a+42)/7 = a/5
(a+42)*5/7 = a
(a+42)*5 = 7a
5a+210 = 7a
2a=210
a=105


哥哥有N元,弟弟有75又5分之1元,各自用去7又2分之1元後,哥哥的錢便等於弟弟的3倍.
例式+答案+驗算

75.2 - 7.5 = 67.7 {弟弟用去錢後剩餘}
67.7 *3 = 203.1 {哥哥用去錢後剩餘}
n = 203.1 + 7.5 = 210.6 {哥哥原來的錢}

驗算
210.6 - 7.5 = 203.1 {哥哥用去錢後剩餘}
203.1 /3 = 67.7 {弟弟用去錢後剩餘}
n = 67.7 + 7.5 = 75.2 {弟弟原來的錢}

爸爸今年38歲,大女比小女大3歲,爸爸的年齡剛好是兩位女兒年齡合計的2倍.
利用方程式求小女兒的年齡. (設年齡是a歳)
例式+答案+驗算

大女: a+3歳
(a+3+a)*2 = 38 {爸爸的年齡是兩位女兒年齡合計的2倍}
2a+3 = 19
2a = 16
a=8

驗算
細女:8歲 大女11歲
2位女兒合共: 11+8 =19歲
38歲 = 19*2

兄弟二人分得糖果50粒,哥哥比弟弟多分6粒.
利用方程式求弟弟得糖幾粒. (設弟弟得糖a粒)
例式+答案+驗算

哥哥: a+6
a+6+a=50 {兄弟二人分得糖果50粒}
2a+6=50
2a=44
a=22

驗算
弟弟: 22
哥哥: 28
22+28=50粒

2007-08-01 01:28:51 補充：
7分之a 6定係講(a 6)/7?係既話就呢個:(a 6)*5/7 = a5a 30 = 7a2a=30a=15

a/7 + 6 = a/5
a/5 - a/7 = 6 (通分母)
(7a - 5a)/(5 x 7) = 6
2a = 6 x (5 x 7)
2a = 210
a = 105

哥哥有N元用去7又2分之1元後 = N - 7又1/2
弟弟有75又5分之1元用去7又2分之1元後 = 75又1/5 - 7又1/2 = 67又7/10
哥哥的錢便等於弟弟的3倍
N - 7又1/2 = 3 ( 67又7/10)
N = 3 ( 67又7/10) + 7又1/2
N = 210又3/5

設小女兒年齡是a歳
大女比小女大3歲 = a + 3歳
爸爸的年齡剛好是兩位女兒年齡合計的2倍 = 2 x [a + (a + 3)] = 38
2 x [2a + 3] = 38
2a + 3 = 19
2a = 19 - 3
2a = 16
a = 16/2
a = 8
小女兒的年齡是8歳

設弟弟得糖a粒
哥哥比弟弟多分6粒 = a + 6粒
兄弟二人分得糖果50粒 = a + (a + 6) = 50
a + (a + 6) = 50
2a + 6 = 50
2a = 50 - 6
2a = 44
a = 44/2
a = 22
弟弟得糖22粒

1.(a+6)/7=a/5
5a+30=7a
a=15
2.n-7 1/2 = 3(75 1/5 - 7 1/2)
n=210.6
3.38=2(a+a+3)
a=8
4.a+a+6=50
a=22