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A = \(\dfrac{25}{1\times6}\) + \(\dfrac{25}{6\times11}\) + \(\dfrac{25}{11\times16}\)+\(\dfrac{25}{16\times21}\)+ \(\dfrac{25}{26\times31}\)
A = 5 \(\times\) ( \(\dfrac{5}{1\times6}\)+\(\dfrac{5}{6\times11}\)+\(\dfrac{5}{11\times16}\)+\(\dfrac{5}{16\times21}\)+\(\dfrac{5}{26\times31}\))
A = 5 \(\times\) ( \(\dfrac{1}{1}\) - \(\dfrac{1}{6}\) + \(\dfrac{1}{6}\) - \(\dfrac{1}{11}\)+ \(\dfrac{1}{11}\)- \(\dfrac{1}{16}\)+ \(\dfrac{1}{16}\)- \(\dfrac{1}{21}\)+ \(\dfrac{1}{26}\)- \(\dfrac{1}{31}\))
A = 5 \(\times\)( 1 - \(\dfrac{1}{31}\))
A = 5 \(\times\) \(\dfrac{30}{31}\)
A = \(\dfrac{150}{31}\)
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\(\dfrac{25x8+25x9+25-25x5}{99+98+97+96}\)
\(=\dfrac{25x\left(8+9+1-5\right)}{390}\)
\(=\dfrac{25x13}{390}\)
\(=\dfrac{25x13}{13x30}\)
\(=\dfrac{5}{6}\)
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125 + 125 + 125 + 125 - 25 - 25 - 25 - 25
= ( 125 - 25 ) + ( 125 - 25 ) + ( 125 - 25 ) + ( 125 - 25 )
= 100 + 100 + 100 + 100
= 100 x 4
= 400
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13 , 25 : 0, 5 + 13 , 25 : 0 , 25 + 13 , 25 : 0 , 125
= 13 , 25 x 2 + 13 , 25 x 4 + 13 , 25 x 8
= 13 , 25 x ( 2 + 8 ) + 13 , 25 x 4
= 13 , 25 x 10 + 43
= 132 , 5 + 43
= 175 , 5
Tham khảo nha !!! Chúc học tốt ~!!
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Các phân số viết theo thứ tự từ lớn đến bé là :
4/25 , 7/25 , 9/25 , 12/25 , 23/25.
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Tính nhanh
= 64 nhân 25 + 35 nhân 25 + 25 nhân 1
= ( 64 + 35 + 1 ) nhân 25
= 100 nhân 25
= 2500
Đây nha
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a) 17 x 25 + 25 x 33 +25 x 50 = 25 x (17 + 33 + 50)
= 25 x 100 = 2500
b) 125 x 15 -25 x 15 = 15 x (125 - 25)
= 15 x 100 = 1500
12,5 x 2 + 12,5 x 4 + 12,5 x 2 + 25
= 12,5 x 2 + 12,5 x 4 + 12,5 x 2 + 12,5 x 2
= 12,5 x (2 + 4 + 2 + 2)
= 12,5 x 10
= 125