so sanh hai phan so 16/51 va 31/90
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Cách 1: Quy đồng mẫu số
\(\frac{31}{40}=\frac{7471}{9640}\)\(;\frac{186}{241}=\frac{7440}{9640}\)
\(\frac{7471}{9640}>\frac{7440}{9640}\)suy ra \(\frac{31}{40}>\frac{186}{241}\)
Cách 2: Quy đồng tử số:
\(\frac{31}{40}=\frac{5766}{7440}\) \(;\frac{186}{241}=\frac{5766}{7471}\)
\(\frac{5766}{7440}>\frac{5766}{7471}\) suy ra \(\frac{31}{40}>\frac{186}{241}\)
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31/90>30/90=1/3=17/51>16/51
=>31/90>16/51
làm nhanh gọn nhẹ !
Ta có:16/51<17/51=1/3=30/90<31/90
=> 16/51<1/3<31/90
Vậy 16/51<31/90
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so sánh
ta có
333444=3334.111=(3334)111
444333=4443.111=(4443)111
So sánh 3334và 4443 ta có
3334=(3.111)4=34 . 1114=81.1114
4443=(4.111)3=43. 1113=64. 1113
Vì 81.1114>64.1113
Suy ra 333444>444333
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Ta có :
\(\frac{2017}{2015}-1=\frac{2}{2015}\) ; \(\frac{31}{29}-1=\frac{2}{29}\)
Vì \(\frac{2}{2015}< \frac{2}{29}\)nên \(\frac{2017}{2015}< \frac{31}{29}\).
2017/2015 = 1,00099....
31/29 = 1,0689....
Vì hàng phần trăm 0 < 6 nên 2017/2015 < 31/29
Kết luận : ....
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\(\frac{16}{51}< \frac{31}{90}\)
16*3=48<51<31*3=93>90
=>16/51 < 31/90