How about 1 / 2 plus 1 / 3 in primary school? How much should it equal? 1 / 8 + 1 / 7 =?

How about 1 / 2 plus 1 / 3 in primary school? How much should it equal? 1 / 8 + 1 / 7 =?

1/2+1/3=3/6+2/6=5/6
1/8+1/7=7/56+8/56=15/56

A simple method for calculating 2800-4-6-8 - -98-100.

4 + 6 + 8 first +100=（4+6+8+…… +96）+97+98+99+100
=（4+96）+（6+94）+…… +（48+50）+97+98+99+100
=23×100+2×197=2300+394=2694
So the original formula = 2800-2694 = 106

A simple method to calculate 1 / 2 * 4 + 1 / 4 * 6 + 1 / 6 * 8 + ····· + 1 / 98 * 100

1/2*4+1/4*6+1/6*8+······+1/98*100
=1/2*(1/2-1/4+1/4-1/6+1/6-1/8+…… +1/98-1/100)
=1/2*(1/2-1/100)
=1/2*49/100
=49/200
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