Bài 1
a, 4209
b, 61,1
c, 217,12
d, 436,88
e, 43763
g, 87,52
Bài 2
a, 133 + 760 + 65 + 42
= ( 133 + 42 ) + ( 760 + 65 )
= 175 + 825
= 1000
b, 14 x 28 + 28 x 36
= 28 x ( 14 + 36 )
= 28 x 50
= 1400
c, 12 x 18 + 14 x 3 - 255 : 17
= 216 + 42 -15
= 258 -15
= 243
d, 68 + 42 x 5 - 625 : 25
= 68 + 210 - 25
= 278 - 25
= 253
e, 18 - 4 x ( 27 -90 + 73 ) : 10
= 18 - 4 x 10 : 10
= 18 - 40 : 10
= 18 - 4
= 14
g, 15 x ( 27 + 18 +6 ) + 15 x ( 23 - 12 )
= 15 x 51 + 15 x 35
= 15 x ( 51 + 35 )
= 15 x 86
= 1296
h, 417 + 235 + 583 + 765
= ( 417 + 583 ) + ( 235 + 765 )
= 1000 + 1000
= 2000
i, 5+8+11+14+...+38+41
k, 49 - 51 + 53 - 55 + 57 - 59 + 61 - 63 + 55