2:
a: \(25,7+9,48+14,3\)
\(=25,7+14,3+9,48\)
\(=40+9,48=49,48\)
b: \(8,24+3,69+2,31\)
\(=8,24+\left(3,69+2,31\right)\)
\(=8,24+6=14,24\)
c: \(8,65+7,6+1,35+0,4\)
\(=\left(8,65+1,35\right)+\left(7,6+0,4\right)\)
\(=10+8=18\)
d: \(5,92+0,44+5,56+4,08\)
\(=\left(5,92+4,08\right)+\left(0,44+5,56\right)\)
\(=10+6=16\)
e: \(7,5+6,5+5,5+4,5+3,5+2,5\)
\(=\left(7,5+2,5\right)+\left(6,5+3,5\right)+\left(5,5+4,5\right)\)
=10+10+10
=30
Bài 2
a) 25,7 + 9,48 + 14,3
= (25,7 + 14,3) + 9,48
= 40 + 9,48
= 49,8
b) 8,24 + 3,69 + 2,31
= 4,24 + (4 + 3,69 + 2,31)
= 4,24 + 10
= 4,24
c) 8,65 + 7,6 + 1,35 + 0,4
= (8,65 + 1,35) + (7,6 + 0,4)
= 10 + 8
= 18
d) 5,92 + 0,44 + 5,56 + 4,08
= (5,92 + 4,08) + (0,44 + 5,56)
= 10 + 6
= 16
e) 7,5 + 6,5 + 5,5 + 4,5 + 3,5 + 2,5
= (7,5 + 2,5) + (6,5 + 3,5) + (5,5 + 4,5)
= 10 + 10 + 10
= 30
