Question

x = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 .

x = 2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18 + 20 .

x = 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 .

Answer 1

X = ( 1+10 ) * 10 / 2 = 11 * 10 / 2 = 110 / 2 = 55

X= (2+20) * 10 /2 = 110

X= (1+19)*10/2= 100

Answer 2

1+2+3+4+5+6+7+8+9+10= (10+1)X10 : 2 = 55

2+4+6+8+10+12+14+16+18+20 = (20+2)x10 : 2 = 110

1+3+5+7+9+11+13+15+17+19 = (19+1) x 10 : 2 = 100

Answer 3

x=55

x=110

x=100

Answer 4

tính nhanh à

 

Answer 5

x=55

x=110

x=100