有3個數分別是A,B,C
已知A,B的平均數是62
B,C的平均數是68
而A,C的平均數是70
求A,B同C的數值分別是多少???
Maths = =
2007-11-28 3:35 am
回答 (5)
2007-11-28 4:29 am
✔ 最佳答案
(A+B)/2=62->A+B=124
->A=124-B...(1)
(B+C)/2=68
->B+C=136
->C=136-B....(2)
(A+C)/2=70...(3)
把門1)和緩2)代入(3),
{(124-B)+(136-B)}/2=70
->124-B+136-B=140
->260-2B=140
->2B=120
->B=60
把B=60代入(1)
A=124-B
->A=124-60
->A=64
把A=64代入(3)
(64+C)/2=70
->64+C=140
->C=76
所以A=64,B=60,C=76.
參考: 自己
2007-11-28 5:15 am
A+B:
62x2
=124
B+C:
68x2
=136
A+C:
70x2
=140
2A+2B+2C:
=(A+B)+(B+C)+(A+C)
=124+136+140
=400
A,B,C的平均數:
400/(3x2)
=400/6
=200/3
=66+(2/3)
=66(2/3)
A:
66(2/3)x3-68x2
=200-136
=64
B:
66(2/3)x3-70x2
=200-140
=60
C:
66(2/3)x3-62x2
=200-124
=76
62x2
=124
B+C:
68x2
=136
A+C:
70x2
=140
2A+2B+2C:
=(A+B)+(B+C)+(A+C)
=124+136+140
=400
A,B,C的平均數:
400/(3x2)
=400/6
=200/3
=66+(2/3)
=66(2/3)
A:
66(2/3)x3-68x2
=200-136
=64
B:
66(2/3)x3-70x2
=200-140
=60
C:
66(2/3)x3-62x2
=200-124
=76
參考: me
2007-11-28 3:42 am
A+B = 62 * 2
A+B = 124
B = 124 - A
B+C = 68 * 2
B+C = 136
(124-A) + C = 136
-A+C = 12 --- (1)
A+C = 70 * 2
A+C = 140 --- (2)
(1) + (2)
2C = 152
C = 76
=> A = 64
=> B = 60
A+B = 124
B = 124 - A
B+C = 68 * 2
B+C = 136
(124-A) + C = 136
-A+C = 12 --- (1)
A+C = 70 * 2
A+C = 140 --- (2)
(1) + (2)
2C = 152
C = 76
=> A = 64
=> B = 60
2007-11-28 3:41 am
(A + B)/2 = 62 --> A + B = 124 ......(1)
(B + C)/2 = 68 --> B + C = 136 ....... (2)
(A + C)/2 = 70 --> A + C = 140 ...... (3)
(1)+(2)+(3), we have
2A + 2B + 2C = 400
A + B + C = 200 ........ (4)
(4) - (2): A = 64
(4) - (3): B = 60
(4) - (1): C = 76
(B + C)/2 = 68 --> B + C = 136 ....... (2)
(A + C)/2 = 70 --> A + C = 140 ...... (3)
(1)+(2)+(3), we have
2A + 2B + 2C = 400
A + B + C = 200 ........ (4)
(4) - (2): A = 64
(4) - (3): B = 60
(4) - (1): C = 76
2007-11-28 3:41 am
(A+B)/2=62
A+B=124----(1)
similarly, B+C=136----(2)
A+C=140-----(3)
(3) - (2): A-B=4 ----(4)
Sub (4) into (1)
2B+4=124
therefore B=60 ,A=64 ,C=76
A+B=124----(1)
similarly, B+C=136----(2)
A+C=140-----(3)
(3) - (2): A-B=4 ----(4)
Sub (4) into (1)
2B+4=124
therefore B=60 ,A=64 ,C=76
參考: me
收錄日期: 2021-04-13 14:35:52
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