Câu1a,tính nhanh
16+(27-7×6)-(947-27×99)
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a) \(16+\left(27-7\cdot6\right)-\left(94\cdot7-27\cdot99\right)\)
\(=16+27-7\cdot6-94\cdot7+27\cdot99\)
\(=16+27\left(1+99\right)-7\left(6+94\right)=16+2700-700=2016\)
b)\(A=\frac{2}{1\cdot4}+\frac{2}{4\cdot7}+\frac{2}{7\cdot10}+...+\frac{2}{97\cdot100}\)
\(=\frac{1}{3}\left(\frac{2}{1}-\frac{2}{4}+\frac{2}{4}-\frac{2}{7}+\frac{2}{7}-\frac{2}{10}+...+\frac{2}{97}-\frac{2}{100}\right)\)
\(=\frac{1}{3}\left(2-\frac{2}{100}\right)=\frac{1}{3}\cdot\frac{99}{50}=\frac{33}{50}\)
a ) 37 x 27 + 63 x 27
= ( 37 + 63 ) x 27
= 100 x 27
= 2700
b ) 1 + 2 + 3 + 4 + ... + 97 + 98 + 99
= ( 99 - 1 ) : 1 + 1
= 99 x ( 99 + 1 ) : 2
= 4950
c ) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + ( 5 + 10 )
= 10 + 10 + 10 + 10 + 15
= 55
\(27\cdot36+73\cdot99+27\cdot14-49\cdot7\)
\(=27\cdot\left(36+14\right)+73\cdot99-49\cdot7\)
\(=27\cdot50+6884=1350+6884=8234\)
\(\dfrac{5^6}{5^4}+2^3\cdot2^2-1^{2017}\)
\(=5^2+2^5-1\)
=25+32-1
=25+31
=56
a) \(\frac{19}{27}+\frac{9}{7}+\frac{6}{27}+\frac{5}{7}+\frac{2}{27}\)
\(=\left(\frac{19}{27}+\frac{6}{27}+\frac{2}{27}\right)+\left(\frac{9}{7}+\frac{5}{7}\right)\)
\(=1+2=3\)
b) \(\frac{2}{7}+\frac{27}{48}+\frac{7}{16}+\frac{45}{63}\)
\(=\frac{2}{7}+\frac{9}{16}+\frac{7}{16}+\frac{5}{7}\)
\(=\left(\frac{2}{7}+\frac{5}{7}\right)+\left(\frac{9}{16}+\frac{7}{16}\right)\)
\(=1+1=2\)
sai rồi bạn ơi
phải là :
(83+27)X7-7x6-7x4
=110x7-7x6-7x4
=7x(110-6-4)
=7x100
=700
\(\dfrac{5x7x99}{27x35x11}\)=\(\dfrac{1x9}{27x1x1}\)=\(\dfrac{1}{3}\)