1/5 + 3/10 + 7/20. 17/20 + 23/30 + 11/60. 7/40 + 11/70 + 13/30

Question

1/5 + 3/10 + 7/20. 17/20 + 23/30 + 11/60. 7/40 + 11/70 + 13/30

Comments

а что означают / ?

Answer 1

1/5+3/10+7/20 = (4*1 + 2*3 +1*7)/20 = (4+6+7)/20 = 17/20

17/20+23/30+11/60 = (3*17 + 2*23 +1*11)/60 = (51+46+11)/60 =108/60
 = 27/15 =9/5

7/40+11/70+13/30 = (21*7 + 12*11 + 28*13)/840 = (147+132+364)/840
= 643/840