Question

tính nhanh

y+2*y+3*y+4*y...+10*y=49,5

Answer 1

=> y*(1+2+3+4+.........+10)=49,5

=> y*(10+1).10:2=49,5

=> y*11.10:2=49,5

=> y*110:2=49,5

=> y*110=49,5*2

=> y=99:110

=> y=0,9

Answer 2

dễ òm à

Answer 3

y+2 x y+3 x y+.....+10 x y=49,5

=>y x (1+2+3+....+10)=49,5

Tứ ->10 có:10-1+1=10(số hạng)

=>1+2+3+...+10=\(\frac{10x\left(10+1\right)}{2}=\frac{10x11}{2}=\frac{110}{2}=55\)

=>y x 55=49,5

=>y=49,5:55=>y=0,9

Answer 4

y+2*y+........+10*y=49,5

(1+2+........+10)*y=49,5

55*y=49,5

y=49,5:55

y=0,9