tính nhanh cho mình nha 

50 - 51 + 40 -41 + 30 -31 + 60

= ( 50 - 41 ) + ( 40 - 31 ) +( 60 - 51 ) + 30

= 9 + 9 + 9 + 30

= 9 x 4 + 30

= 36 + 30

= 66

Hok tốt !!

mình đang cần gấp

Co h khong

25 x 27 + 25 x 10 + 25 x 13 + 25 x 2

= 25 x ( 27 + 10 + 13 + 2 )

= 25 x 52

=1300

X x 5 + X x 3 + X x 2 = 160

X x (5 + 3 + 2) = 160

X x 10= 160

X = 160 : 10

X = 16

50% của x = 50% x 16 = 8 

X*(5+3+2)=160

X=160/10=16

50/100 của X=8

\(2011,2012\times2000\times\left(\frac{5}{6}-\frac{1}{3}-50\%\right)\times1234+10\)

\(=2011,2012\times2000\times\left(\frac{5}{6}-\frac{1}{3}-\frac{50}{100}\right)\times1234+10\)

\(=2011,2012\times2000\times\left(\frac{5}{6}-\frac{1}{3}-\frac{1}{2}\right)\times1234+10\)

\(=2011,2012\times2000\times\left(\frac{5}{6}-\frac{2}{6}-\frac{3}{6}\right)\times1234+10\)

\(=2011,2012\times2000\times0\times1234+10\)

\(=0+10\)

\(=10\)

_Chúc bạn học tốt_

\(2011,2012.2000.\left(\frac{5}{6}-\frac{1}{3}-50\%\right).1234+10\)

\(=2011,2012.2000.\left(\frac{5-2-3}{6}\right).1234+10\)

\(=2011,2012.2000.0.1234+10\)

\(=0+10\)

\(=0 \)

=36

chuyển \(\frac{2}{20}=\frac{1}{10}\) rồi đến 3/30,4/40,... rồi cứ thế tiếp nhưng ngoại trừ 1/10

Đây mà toán lớp 5 à.

Áp dụng công thức

\(\frac{1}{1+2+...+n}=\frac{1}{\frac{n\left(n+1\right)}{2}}=\frac{2}{n\left(n+1\right)}\)  ta được

\(\frac{1}{1+2}+\frac{1}{1+2+3}+...+\frac{1}{1+2+....+50}\)

\(=\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{50.51}\)

\(=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{50}-\frac{1}{51}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{51}\right)=\frac{49}{51}\)

Ta có : \(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+.......+\frac{1}{1+2+3+......+50}\)

\(=\frac{1}{\frac{2.3}{2}}+\frac{1}{\frac{3.4}{2}}+\frac{1}{\frac{4.5}{2}}+......+\frac{1}{\frac{50.51}{2}}\)

\(=\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+......+\frac{2}{50.51}\)

\(=2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+......+\frac{1}{50.51}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+......+\frac{1}{50}-\frac{1}{51}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{51}\right)\)

\(=2.\frac{1}{2}-2.\frac{1}{51}\)

\(=1-\frac{2}{51}=\frac{49}{51}\)

tìm a

a=2 mũ 41 nhân 5 mũ 38 

 a = 2⁴¹ . 5³⁸

a) \(\frac{637\times527-189}{526\times637+448}\)

\(=\frac{637\times\left(526+1\right)-189}{526\times637+448}\)

\(=\frac{637\times526+637-189}{526\times637+448}\)

\(=\frac{637+526+448}{526\times637+448}\)

\(=1\)

b) \(\frac{64\times50+44\times100}{27\times38+146\times19}\)

\(=\frac{50\times\left(64+44\times2\right)}{19\times\left(27\times2+146\right)}\)

\(=\frac{50\times\left(64+88\right)}{19\times\left(54+146\right)}\)

\(=\frac{50\times152}{19\times200}\)

\(=\frac{152}{19\times4}\)

\(=\frac{38}{19}\)

\(=\frac{2}{1}\)

\(=2\)