rút gọn 250/750;216/270
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Câu 1:15/35=3/7
216/270=4/5
250/750=1/3
Câu 2:8/18,12/27,16/36,20/45,24/54
Câu 3:1/2=2/4=3/6=4/8=5/10
Câu 4:2×3×5/2×7×5=30/70=3/7
Tk mình nhé bn!
Bài 1:
\(\frac{15}{35}=\frac{3}{7}\)
\(\frac{216}{270}=\frac{4}{5}\)
\(\frac{250}{750}=\frac{1}{3}\)
Bài 2:
5 phân số bằng phân số \(\frac{4}{9}\) là: \(\frac{8}{18};\frac{12}{27};\frac{16}{36};\frac{20}{45};\frac{24}{54}\)
Bài 3:
\(\frac{1}{2};\frac{2}{4};\frac{3}{6};\frac{4}{8};\frac{5}{10}\)
Bài 4:
\(\frac{2x3x5}{2x7x5}=\frac{3}{7}\)
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a) \(250 + 250 × 2 = 250 + 500 = 750 \\ (250 + 250) × 2 = 500 × 2 = 1 000\)
b)\( 750 – 50 × 5 = 750 – 250 = 500\\
(750 – 50) × 5 = 700 × 5 = 3 500\)
c) \(210 × 4 – 4 × 210 = 840 – 840 = 0\\
3 × (270 : 9) × 0 = 0\)
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2B = 2 + 1 + 1/2 + 1/2^2 + ... + 1/2^249
2B - B = (2 + 1 + 1/2 + 1/2^2 + ... + 1/2^249) - (1 + 1/2 + 1/2^2 + 1/2^3 + ... + 1/2^250)
B = 2 - 1/2^250
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x + 350 = 750 + 250
x + 350 = 1000
x = 1000 - 350
x = 650 ai k mk,mk k lại
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Ta có
\(B=1+\frac{1}{2}+.....+\frac{1}{2^{250}}\)
\(\Rightarrow2B=2+1+....+\frac{1}{2^{251}}\)
\(\Rightarrow2B-B=\left(2+1+....+\frac{1}{2^{251}}\right)-\left(1+\frac{1}{2}+.....+\frac{1}{2^{250}}\right)\)
\(\Rightarrow B=2-\frac{1}{2^{251}}\)
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x+1000-100+100=250+750
x+1000-100+100=1000
x+1000-100=1000-100
x+1000-100=900
x+1000=900+100
x+1000=1000
x=1000-1000
x=0
\(\frac{250}{750}=\frac{250:250}{750:250}=\frac{1}{3}\) ; \(\frac{216}{270}=\frac{216:54}{270:54}=\frac{4}{5}\)
mình cảm ơn