3-2 + 4-3 + 5-4 + 6-5 + .+ 51-50
1+2 1+2+3 1+2+3+4 1+2+3+4+5 1+2+3…+50
=1-2/3+2/3-1/2+1/2-2/5+2/5-1/3+.+1/25-2/51
=1-2/51
=49/51
3-2 + 4-3 + 5-4 + 6-5 + .+ 51-50
1+2 1+2+3 1+2+3+4 1+2+3+4+5 1+2+3…+50
=1-2/3+2/3-1/2+1/2-2/5+2/5-1/3+.+1/25-2/51
=1-2/51
=49/51