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a) 27x6 = 3*9*6 = 162
b) 99x4 = 11x9x4 = 396
c) 125x16 = 5x5x5x4x4=2000
![](https://rs.olm.vn/images/avt/0.png?1311)
16.19
=16.(20-1)
=320-16
=304
46.99
=46.(100-1)
=4600-46
=4554
35.98
=35.(100-2)
=3500-70
=3430
16.(20-1)=320-16=304
46.(100-1)=4600-46=4554
35.(100-2)=3500-70=3430
![](https://rs.olm.vn/images/avt/0.png?1311)
13.19=13.(20-1)=13.20-1=260-1=259
46.99=46.(100-1)=46.100-1=4600-1=4599
35.98=35.(100-2)=35.100-2=3500-2=3498
k mình nha
16.19 = 16 (20-1) = 16.20 - 16.1 = 320 - 16 = 304
46.99 = 49. (100 - 1) = 49.100- 49.1 = 4900 - 49 = 4851
35. 98 = 35. (100-2) = 35.100 - 35.2 = 3500 - 70 = 3430
![](https://rs.olm.vn/images/avt/0.png?1311)
16.(20-1)=320-16=304
46.99=46.(50-1)=2300-46=2554
35.(100-2)=3500-70=3430
16 . 19 = 16(20 - 1) = 320 - 16 = 304;
46 . 99 = 46(100 - 1) = 4600 - 46 = 4554;
35 . 98 = 35(100 - 2) = 3500 - 70 = 3430.
![](https://rs.olm.vn/images/avt/0.png?1311)
16 . 19 = 16(20 - 1) = 320 - 16 = 304;
46 . 99 = 46(100 - 1) = 4600 - 46 = 4554;
35 . 98 = 35(100 - 2) = 3500 - 70 = 3430.
![](https://rs.olm.vn/images/avt/0.png?1311)
a)\(=16\cdot\left(20-1\right)\)\(=320-16=304\)
b)\(=46\cdot\left(100-1\right)=4600-46=4554\)
c)\(=35\cdot\left(100-2\right)=3500-70=3430\)
đúng nhớ
16.19 = 16.(20-1) = 16.20 - 16 = 320 - 16 = 304
46.99 = 46.(100-1) = 46.100 - 46 = 4600 - 46 = 4554
35.98 = 35.(100-2) = 35.100 - 35.2 = 3500 - 70 = 3430
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 38+88=(30+80)+(8+8)
=110+16
=128 (nhẩm đó)
b,97+87= (90+80)+(7+7)
=170+14
=184 (nhẩm thật)
c, 36+76=(30+70)+(6+6)
=100+12
=112 (nhẩm thiệt)
A) 38+88=(30+80)+(8+8)
=110+16
=128
B)97+87= (90+80)+(7+7)
=170+14
=184
C) 36+76=(30+70)+(6+6)
=100+12
=112
![](https://rs.olm.vn/images/avt/0.png?1311)
Giải:
a) \(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{4}\right).\left(1-\dfrac{1}{5}\right)\)
\(=\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}\)
\(=\dfrac{1.2.3.4}{2.3.4.5}\)
\(=\dfrac{1}{5}\)
b) \(\left(1-\dfrac{3}{4}\right).\left(1-\dfrac{3}{7}\right).\left(1-\dfrac{3}{10}\right).\left(1-\dfrac{3}{13}\right).....\left(1-\dfrac{3}{97}\right).\left(1-\dfrac{3}{100}\right)\)
\(=\dfrac{1}{4}.\dfrac{4}{7}.\dfrac{7}{10}.\dfrac{10}{13}.....\dfrac{94}{97}.\dfrac{97}{100}\)
\(=\dfrac{1.4.7.10.....94.97}{4.7.10.13.....97.100}\)
\(=\dfrac{1}{100}\)
Chúc bạn học tốt!
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1. \(\left(\dfrac{1}{99}+\dfrac{12}{999}-\dfrac{123}{9999}\right).\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\)
\(=\left(\dfrac{1}{99}+\dfrac{12}{999}-\dfrac{123}{9999}\right).0\)
\(=0\)
97 x 99
= 97 x (100 - 1)
= 97 x 100 - 97
= 9700 - 97
= 9603
a) 97x99
=(99-2)x99
=99x99-2x99
=9801-198
=9603.
K nhé các bạn ơi.