更新1:
A.78 B.90 C105 D.117 Explan your answer briefly
更新2:
four arithmetic means are inserted between 12 and 27 即是頭4个term的數值是分別介乎於 12-27 . then the sum of the four arithmetic 即是頭4个term相加的數值一定不是 D.117 因27+27+27+27=108.即答案只會是A ,B, C
更新3:
Then 我知first term是12,但我不知common difference是咩,於是我 Assume d=1 12+1+1+1=15 Assume d=2 12+2+2+2=18 Assume d=3 12+3+3+3=21 Assume d=4 12+4+4+4=24 Assume d=5 12+5+5+5=27 thus, d=5 我咁唸對不對??????????????????????????????????????????????????????
