Đặt tính rồi tính
41 326 + 29 548 56 695 – 24 968 12 309 x 7 36 730 : 5
Đặt tính rồi tính:
43 + 23 60 + 38 41 + 7
87 - 55 72 - 50 56 - 5
- Đặt tính : Viết phép tính sao cho các chữ số cùng hàng thẳng cột với nhau.
- Tính : Cộng hoặc trừ các số lần lượt từ phải sang trái.
1)Tính:
a) A=1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
b) B=(3/4)(8/9)(15/16)(24/25)(35/36)(48/49)(63/64)
c) C=1/4+1/12+1/36+1/108+1/324+1/92
\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+...+\frac{89}{90}\)
\(=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+...+1-\frac{1}{90}\)
\(=9-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=9-\frac{9}{10}=\frac{81}{10}\)
Đặt tính rồi tính:
54 x 3=
309 x 2=
75 : 5=
845 : 7=
Đặt tính rồi tính:
54 x 3= 162
309 x 2= 618
75 : 5= 15
845 : 7= 120 (dư 5)
Đặt tính rồi tính (theo mẫu):
a)105 x 5 242 x 4 96 x 6
............ ............ ...........
............ ............ ...........
............ ............ ...........
b)940 : 5 847 : 7 309 : 3
............ ............ ...........
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Đặt tính rồi tính.
457 + 452 326 + 29 762 + 184 546 + 172
\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{457}\\{452}\end{array}}\\\hline{\,\,\,907}\end{array}\) \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{326}\\{\,\,29}\end{array}}\\\hline{\,\,\,355}\end{array}\)
\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{762}\\{184}\end{array}}\\\hline{\,\,\,946}\end{array}\) \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{546}\\{172}\end{array}}\\\hline{\,\,\,718}\end{array}\)
Tính giá trị biểu thức
A=1/4+1/12+1/36+1/108+1/324+1/972
B=1/2+5/6+11/12+19/20+29/30+41/42+55/56
\(A=\frac{1}{4}+\frac{1}{12}+\frac{1}{36}+\frac{1}{108}+\frac{1}{324}\)
\(3A=3\left(\frac{1}{4}+\frac{1}{12}+\frac{1}{36}+\frac{1}{108}+\frac{1}{324}+\frac{1}{972}\right)\)
\(3A=\frac{3}{4}+\frac{3}{12}+\frac{3}{36}+\frac{3}{108}+\frac{3}{324}+\frac{3}{927}\)
\(3A=\frac{3}{4}+\frac{1}{4}+\frac{1}{12}+\frac{1}{36}+\frac{1}{108}+\frac{1}{324}\)
\(2A=3A-A\)
\(2A=\left(\frac{3}{4}+\frac{1}{4}+\frac{1}{12}+\frac{1}{12}+\frac{1}{36}+\frac{1}{108}+\frac{1}{324}\right)-\left(\frac{1}{4}+\frac{1}{12}+\frac{1}{36}+\frac{1}{108}+\frac{1}{324}+\frac{1}{972}\right)\)
\(2A=\frac{3}{4}-\frac{1}{927}\)
\(2A=\frac{729-1}{972}=\frac{728}{972}=\frac{182}{243}\)
\(A=\frac{182}{243}:\frac{1}{2}\)
\(A=\frac{364}{243}\)
A=1/4+1/12+1/36+1/108+1/324+1/972
=243/972+81/972+27/972+9/972+3/972+1/972
=364/972
=91/243
\(B=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}\)
\(B=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+\left(1-\frac{1}{20}\right)+\left(1-\frac{1}{30}\right)+\left(1-\frac{1}{42}\right)+\left(1-\frac{1}{56}\right)\)
\(B=1.9-\left(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{56}\right)\)
\(B=9-\left[\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+...+\left(1-\frac{1}{56}\right)\right]\)
\(B=9-\left(1-\frac{1}{56}\right)\)
\(B=9-\frac{55}{56}\)
\(B=\frac{449}{56}\)
Đặt tính rồi tính
a. 968 753 + 15 247
b. 68 753 – 12 568
a. 968 753 + 15 247
+ 968753 15247 984000
b. 68 753 – 12 568
− 68753 12568 56185
Đặt tính rồi tính.
a) 36 + 7 5 + 48 29 + 64
b) 73 – 6 82 – 57 91 – 85
a) \(36+7=43\)
\(5+48=53\)
\(29+64=93\)
b) \(73-6=67\)
\(82-57=25\)
\(91-85=6\)
a: 36+7=43
5+48=53
29+64=95
b: 73-6=67
82-57=25
91-85=6