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\(a,\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\\ =\dfrac{3\times4\times2\times15}{2\times5\times3\times4}\\ =\dfrac{3\times4\times2\times5\times3}{2\times5\times3\times4}\\ =3\)
\(b,\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\\ =\dfrac{6\times5\times7\times7\times8}{7\times8\times3\times6\times5}\\ =\dfrac{7}{3}\)
a) \(\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\)
\(=\left(\dfrac{3}{2}\times\dfrac{2}{3}\right)\times\left(\dfrac{4}{5}\times\dfrac{15}{4}\right)\)
\(=1\times3\)
\(=3\)
b) \(\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\)
\(=\left(\dfrac{6}{7}\times\dfrac{7}{6}\right)\times\left(\dfrac{5}{8}\times\dfrac{8}{5}\right)\times\dfrac{7}{3}\)
\(=1\times1\times\dfrac{7}{3}\)
\(=\dfrac{7}{3}\)
Chúc bạn học tốt
TL :
1) 112 x 5 x 2
= 112 x 10
=1120
2) 2 x 247 x 5
= 247 x 10
= 2470
3) 2 x 4 x 3 x 5
= 12 x 10
= 120
4) 20 x 7 x 5 x 8
= 100 x 56
= 5600
5) 25 x 35 x 4
= 100 x 35
= 3500
6) 47 x 7 + 47 x 3
= 47 x ( 7 + 3 )
= 47 x 10
= 470
7) 5 x 7 x 9 x 2
= 10 x 63
= 630
8) 125 x 9 x 7 x 8
= 1000 x 63
= 63000
9) 4 x 97 x 25
= 100 x 97
= 9700
10) 8 x 9 x 10 ( chắc thế )
= 80 x 9
= 720
11) 240 x 24 + 240 x 24
= 24 x ( 240 + 240 )
= 24 x 480
= 11520
12) 27 x 2 + 27 x 3 + 27 x 5
= 27 x ( 2 + 3 + 5 )
= 27 x 10
= 270
13) 48 x 4 + 48 x 3 + 48 x 2 + 48
= 48 x 4 + 48 x 3 + 48 x 2 + 48 x 1
= 48 x ( 4 + 3 + 2 + 1 )
= 48 x 10
= 480
14) 247 x 36 + 247 x 64
= 247 x ( 36 + 64 )
= 247 x 100
= 24700
15) 76 x 6 + 76 x 4
= 76 x ( 6 + 4 )
= 76 x 10
= 760
16) 249 x 101 - 249
= 249 x 101 - 249 x 1
= 249 x ( 101 - 1 )
= 249 x 100
= 24900
Mong các ban cho tui 10 cái T I C K
~HT~
1/2 + 2/3 - 3/4 * 4/5 * 5/6 * 6/7 * 7/8 * 8/9 *...* 29/30 : 6/10
= 1/2 + 2/3 - 1/10 : 6/10
= 1/2 + 2/3 - 1/6
= 1
(6 x 5 + 7 - 37) x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= (30 + 7 - 37) x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= 0 x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= 0
\(\frac{9}{10}+\frac{7}{9}+\frac{5}{8}+\frac{3}{7}+\frac{3}{5}+\frac{2}{5}+\frac{4}{7}+\frac{3}{8}+\frac{2}{9}+\frac{1}{10}\)
= \(\left(\frac{9}{10}+\frac{1}{10}\right)+\left(\frac{7}{9}+\frac{2}{9}\right)+\left(\frac{5}{8}+\frac{3}{8}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)
= \(\frac{10}{10}+\frac{9}{9}+\frac{8}{8}+\frac{7}{7}+\frac{5}{5}\)
= \(1+1+1+1+1\)
= \(1\times5\)
= \(5\)
Gọi A là tổng của 9/10 + 7/9 + 5/8 + 3/7 + 3/5 + 2/5 + 4/7 + 3/8 + 2/9 + 1/10, ta có :
A = 9/10 + 7/9 + 5/8 + 3/7 + 3/5 + 2/5 + 4/7 + 3/8 + 2/9 + 1/10
A = (9/10 + 1/10) + (7/9 + 2/9) + (5/8 + 3/8) + (3/7 + 4/7) + (3/5 + 2/5)
A = 1 + 1 + 1 + 1 + 1
A = 5
5/4
= 5/8 x (9/7 + 5/7)
= 5/8 x 12/7
= 15/14