Question

Calculate and write the result by decimal number: 1/2*3+1/3*4+1/4*5+...+1/9*10

Answer 1

= 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ... + 1/9 - 1/10

= 1/2 - 1/10

= 2/5