2 câu trả lời
1 + 2 + 3 + 4+ 5 + 6 + 7 + 8 + 9 + 10
= (1 + 10) + (2 + 9) + (3 + 8) + (4 + 7) + (5 + 6)
= 11 + 11 + 11 + 11 + 11
= 11 x 5 = 55
1 + 2 + 3 + 4+ 5 + 6 + 7 + 8 + 9 + 10
= (1 + 10) + (2 + 9) + (3 + 8) + (4 + 7) + (5 + 6)
= 11 + 11 + 11 + 11 + 11
= 11 x 5 = 55
