Bài 1:
$\frac{5}{9}$ x $\frac{2}{7}$ = $\frac{5x2}{9x7}$ = $\frac{10}{63}$
$\frac{2}{3}$ + $\frac{5}{6}$ = $\frac{4}{6}$ + $\frac{5}{6}$ = $\frac{9}{6}$ = $\frac{3}{2}$
5 - $\frac{13}{17}$ = $\frac{5}{1}$ - $\frac{13}{17}$ = $\frac{85}{17}$ - $\frac{13}{17}$ = $\frac{72}{17}$
3 : $\frac{9}{10}$ = $\frac{3}{1}$ : $\frac{9}{10}$ = $\frac{3}{1}$ x $\frac{10}{9}$ = $\frac{30}{9}$ = $\frac{10}{3}$
Bài 2:
a) 384,49
- 35,35
-------------
419,84
.........................................
b) 165,50
- 35,62
-------------
129,88
..........................................
c) 235,05
x 4,2
------------
47010
94020
-------------
987,210
...........................................
d) 9,125 : 2,5 = 3,65
...........................................
e) 34678
+ 9231
------------
43909
...........................................
g) 98020
- 32451
------------
65569
...........................................
h) 1482
x 402
-----------
2964
5928
-----------
595764
.............................................
i) 9823 : 45 = 218,2888889
Bài 3:
a) x - $\frac{1}{6}$ = $\frac{1}{2}$ + $\frac{1}{3}$
x - $\frac{1}{6}$ = $\frac{5}{6}$
x = $\frac{5}{6}$ + $\frac{1}{6}$
x = $\frac{6}{6}$
x = 1
b) x + $\frac{1}{8}$ = $\frac{1}{2}$ - $\frac{1}{3}$
x + $\frac{1}{8}$ = $\frac{1}{6}$
x = $\frac{1}{6}$ - $\frac{1}{8}$
x = $\frac{1}{24}$
c) x : $\frac{1}{2}$ = $\frac{2}{3}$ x $\frac{3}{4}$
x : $\frac{1}{2}$ = $\frac{1}{2}$
x = $\frac{1}{2}$ x $\frac{1}{2}$
x = $\frac{1}{4}$
Bài 4: (Hình 3)
a) 10,5m = 1050cm
b) 10,5m² = 105000cm²
Bài 5:
a) 48,25 + 12,72 + 51,75 + 87,28
= (48,25 + 51,75) + (12,72 + 87,28)
= 100 + 100
= 200
b) 0,087 + 1,123 + 0,913 + 0,877
= (0,087 + 0,913) + (1,123 + 0,877)
= 1 + 2
= 3
