小六方程式2題

y/3 + y/4 = 7/8

(y/3 + y/4 )x 24 = 7x24/8

8y+6y=21

14y=21

y=3/2//





10 = 5a/6+55

2=a/6+11

12=a+66

66-12=-a

a=-54//

2) 3分之y + 4分之y = 8分之7

y/3+y/4=7/8
4y/12+3y/12=7/8
7y/12=7/8
7y=7/8×12
7y=21/2 (或10.5)
y=21/2÷7 (或10.5÷7)

答案:
以假分數表示:y=3/2
以帶分數表示:y=1又2分之1
以點數表示:y=1.5

3) 10 = 6分之5a+55

10=5a/6+55
10-55=5a/6
-45=5a/6
-45×6=5a
-270=5a
-270÷5=a

答案:
a=-54

y/3 + y/4 = 7/8

(y/3 + y/4 )x 24 = 7x24/8

8y+6y=21

14y=21

y=3/2//
10 = 5a/6+55

2=a/6+11

12=a+66

66-12=-a

a=-54//

2) y/3 +y/4 = 7/8
通分.. ( 3 和 4 的L.C.M 是12)
4y/12+ 3y/12 = 7/8
7y/12 = 7/8
7y = 7/8 x 12
7y = 21/2
y = 21/2 ÷ 7
y = 3/2 or 1.5

3) 10 = (5a+55)/6
10x 6 = (5a+55)/6 x 6
60 = 5a +55
5a = 60-55
5a = 5
a = 5/5
a =1

2008-02-12 20:34:07 補充：
question no.2 除了通分, 也可將兩邊乘12 or 24.

2)1又２分之1 3) a=負54

y=3/2
a=1

3) 10 = 6分之5a+55

a=1