Question

Tính nhanh: (1/2+1/3+1/4+1/5+1/6+1/7)−(1/3+1/4+1/5+1/6+1/7+1/8)

Answer 1

(1/2+1/3+1/4+1/5+1/6+1/7)−(1/3+1/4+1/5+1/6+1/7+1/8)

= (1/2+1/8 )+(1/4+1/6 )+(1/6+1/4)−(1/3+1/7 )-(1/5 + 1/5 )

= 1/10 +1/10 +1/10 +1/10 -1/10 

= 4/10 = 2/5

k mk na <3

Answer 2

1/2 + ( 1/3 - 1/3 ) + ( 1/4 - 1/4 ) + ( 1/5 -1/5 ) + ( 1/6 - 1/6 ) + ( 1/7 - 1/7 ) + 1/8

= 1/2 + 0 + 1/8

= 5/8

Answer 3

= 1/2 - 1/8 = 3/8

Answer 4

= 1/2 -1/8- 3/8