標題:
Maths = =
發問:
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???
最佳解答:
(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.
其他解答:
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|||||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)/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|||||(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
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