Question

BT2: Tính nhanh

3) \(58.\left(3\dfrac{1}{29}-2\dfrac{1}{58}\right):\dfrac{1}{3}\)

4) \(A=1\dfrac{1}{2}.1\dfrac{1}{3}.1\dfrac{1}{4}.1\dfrac{1}{5}\)

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Answer 1

3) \(58\left(3\dfrac{1}{29}-2\dfrac{1}{58}\right):\dfrac{1}{3}\)

\(=58\left(\dfrac{88}{29}-\dfrac{117}{58}\right)\cdot3\\ =\left(58\cdot\dfrac{88}{29}-58\cdot\dfrac{117}{58}\right)\cdot3\)

\(=\left(176-117\right)\cdot3\\ =59\cdot3\\ =177\)

4) \(A=1\dfrac{1}{2}\cdot1\dfrac{1}{3}\cdot1\dfrac{1}{4}\cdot1\dfrac{1}{5}\)

\(=\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot\dfrac{5}{4}\cdot\dfrac{6}{5}\\ =\dfrac{3\cdot4\cdot5\cdot6}{2\cdot3\cdot4\cdot5}\\ =\dfrac{6}{2}\\ =3\)