Đáp án:
Giải thích các bước giải:
1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
= 1/10 + 2/10 + 3 /10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10
= ( 1/10 + 9/10 ) +( 2/10 + 8/10 ) + ( 3 /10 + 7/10 ) + ( 4/10 + 6/10 ) + 5/10
= 10/10 + 10/10 + 10/10 + 10/10 + 5/10
= 45/10 = 9/2