Tính hợp lý:12x67+33x12-600:3
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33 : 313 + 50 : 52 = 3-10 + 25 = \(\frac{1}{59049}\) + 25 = \(\frac{1476226}{59049}\)
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\(\frac{27\times18+27\times103-120\times27}{15\times33+33\times12}\)
\(=\frac{27\times\left(18+103-120\right)}{\left(15+12\right)\times33}\)
\(=\frac{27\times1}{27\times33}\)
\(=\frac{1}{891}\)
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Chiếu một tia sáng từ không khí vào nước thì góc tới phải lớn hơn góc khúc xạ. Nếu góc tới là 600 thì kết quả góc khúc xạ r = 40030’ là hợp lý
→ Đáp án B
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\(1\frac{13}{15}.0,75-\left(\frac{104}{195}+25\%\right).\frac{24}{47}-3\frac{12}{13}:3\)
\(=\frac{28}{15}.\frac{3}{4}-\left(\frac{8}{15}+\frac{1}{4}\right).\frac{8}{9}-\frac{51}{13}.\frac{1}{3}\)
\(=\frac{7}{5}-\left(\frac{32}{60}+\frac{15}{60}\right).\frac{8}{9}-\frac{17}{13}\)
\(=\frac{7}{5}-\frac{47}{60}.\frac{8}{9}-\frac{17}{13}\)
\(=\frac{7}{5}-\frac{94}{135}-\frac{17}{13}\)
\(=\frac{-212}{351}\)
Tự quy đồng
\(2\frac{3}{4}.\left(-0,4\right)-1\frac{3}{5}.2,75+\left(-1,2\right):\frac{4}{11}\)
\(=\frac{11}{4}.\frac{-2}{5}-\frac{8}{5}.\frac{11}{4}-\frac{6}{5}.\frac{11}{4}\)
\(=\frac{11}{4}.\left(\frac{-2}{5}-\frac{8}{5}-\frac{6}{5}\right)\)
\(=\frac{11}{4}.\frac{-16}{5}\)
\(=\frac{-44}{5}=-8\frac{4}{5}\)
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1. Q=165+247+528+125+315
= 100+60+5+200+40+7+500+20+8+100+20+5+300+10+5
= ( 100+200+500+100+300) + ( 60+40+20+20+10 ) +( 5+7+8+5+5 )
= 1200+150+30
=1280
R=1234+5678+8+80
=1000+200+30+4+5000+600+70+8+8+80
= ( 1000+5000) + ( 200+600 ) + (30+70+80) + ( 4+8+8)
=6000+800+180+20
=7000
Ta có :
12 x 67 + 33 x 12 - 600 : 3
= 12 x ( 67+ 33 ) - 200
= 12 x 100 - 2 x 100
= ( 12 - 2 ) x 100
= 10 x 100
= 1000