Tìm y biết: (y- \(\dfrac{1}{2}\)): (\(\dfrac{1}{2}\)+ \(\dfrac{1}{6}\) + \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\)+ ... + \(\dfrac{1}{90}\)) = \(\dfrac{1}{3}\)
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}=\)
Tính nhanh: \(\dfrac{1}{2}\)+ \(\dfrac{1}{6}\)+ \(\dfrac{1}{12}\)+ \(\dfrac{1}{20}\) + ... + \(\dfrac{1}{90}\)
x + \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}=\dfrac{47}{42}\)
Tính nhanh
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\)
VÒNG 2
Bài 1: Mèo con nhanh nhẹn
\(\dfrac{1}{2}\) + \(\dfrac{1}{12}\) | 2 + \(\dfrac{1}{6}\) | \(\dfrac{1}{20}\) | 1 - \(\dfrac{1}{9}\) | |
\(\dfrac{1}{15}\) + \(\dfrac{2}{15}\) | \(\dfrac{1}{2}\) + \(\dfrac{2}{3}\) | \(\dfrac{7}{12}\) | \(\dfrac{4}{12}\) | |
\(\dfrac{9}{14}\)+ \(\dfrac{1}{14}\) | 1 + \(\dfrac{1}{6}\) | \(\dfrac{1}{4}\) - \(\dfrac{1}{5}\) | \(\dfrac{1}{3}\) - \(\dfrac{2}{9}\) | |
\(\dfrac{3}{2}\) + \(\dfrac{2}{3}\) | \(\dfrac{1}{5}\) | 1 - \(\dfrac{8}{9}\) | ||
\(\dfrac{5}{7}\) | 1 - \(\dfrac{2}{3}\) | \(\dfrac{1}{3}\) + \(\dfrac{5}{9}\) |
Bài 2 Tìm y
a) \(\dfrac{1}{2}-2xy=\dfrac{9}{20}\) b)\(\dfrac{3}{5}:\dfrac{4}{3}:y=2+\dfrac{7}{10}\) c) y + y x\(\dfrac{3}{2}-y\) x \(\dfrac{1}{2}=\dfrac{1}{10}\)
\(\dfrac{3}{2}\) + ( \(\dfrac{4}{5}\) : X - \(\dfrac{1}{20}\) ) = 4
tính 20% + \(\dfrac{2}{3}\) +1.8+ 2\(\dfrac{1}{3}\)
Bài 1:
\(a,\dfrac{1}{5}+\dfrac{1}{10}+\dfrac{1}{20}+\dfrac{1}{40}+...............+\dfrac{1}{1280}\)
\(b,\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}+..............+\dfrac{1}{59049}\)
\(c,\dfrac{1}{2}\times3+\dfrac{1}{3}\times4+\dfrac{1}{4}\times5+\dfrac{1}{5}\times6\)