Question

x+(x+1)+(x+2)+...+(x+30)=1240

Answer 1

Lời giải:

$x+(x+1)+(x+2)+....+(x+30)=1240$

$(x+x+...+x)+(0+1+2+...+30)=1240$

$31\times x+465=1240$

$31\times x=1240-465=775$

$x=775:31=25$