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jilin1960 發表於 15-5-23 14:34
Justin wrote 6numbers.the average of first 4 numbers is 30 more than the average of the last 2 numbe ... Let the 6 numbers be A, B, C, D, E and F.
(A+B+C+D)/4 = (E+F)/2 + 30 ......................... (1)
(A+B+C+D)+(E+F)=1770 ......................... (2)
E=186 .................... .................... .................. (3)
(1) -> (A+B+C+D) = 2(E+F) + 120 .................(4)
Sub (4) into (2) -> 2(E+F) + 120 + (E+F) = 1770
3(E+F) = 1650
E+F=550
F = 550 - E = 550 -186 = 364
Therefore, the sixth number is 364.
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