Question

tính nhanh nek mn

\(1\dfrac{1}{3}\times1\dfrac{1}{8}\times1\dfrac{1}{15}\times1\dfrac{1}{24}\times.....\times1\dfrac{1}{99}\)

Answer 1

 

=4/3 x 9/8 x 16/15 x 25/24x.....x100/99 =2x2x3x3x4x4x5x5x.....x10x10/1x3x2x4x3x5x4x6x....x9x11

=(2x3x4x5x....x10 ) x (2x3x4x5x...x10) / (1x2x3x4x....x9 ) x (3x4x5x...x11)

=10x2/11 =20/11

Answer 2

\(\dfrac{4}{3}\times\dfrac{9}{8}\times\dfrac{16}{15}\times\dfrac{25}{24}\times.....\times\dfrac{100}{99}\)

\(\dfrac{2x2x3x3x4x4x5x5x.....x10x10}{1x3x2x4x3x5x4x6x...9x11}\)

\(=\dfrac{10x2}{11}=\dfrac{20}{11}\)