* 24 x 5 + 24 x 3 + 24 x 2

= 24 x (5 + 3 + 2)

= 24 x 10

= 240

240 NHÉ -...- 

DỄ THẾ CŨNG HỎI

Sửa đề:

24/(3×9) + 24/(9×15) + 24/(15×21) + ... + 24/(57×63)

= 24 × 1/6 × (1/3 - 1/9 + 1/9 - 1/15 + 1/15 - 1/21 + ... + 1/57 - 1/63)

= 4 × (1/3 - 1/63)

= 4 × 20/63

= 80/63

Chỗ \(\dfrac{24}{9\times5}\) là sao em nhỉ? đã đúng đề chưa thế em

\(2\times169\times12-3\times68\times8-24\)

\(=24\times169-24\times68-24\)

\(=24\times\left(169-68-1\right)\)

\(=24\times100=2400\)

\(a.24.64+36.24-100.24\)

\(=24.\left(64+36-100\right)\)

\(=24.0\)

\(=0\)

\(b.5.4^2-16:2^2\)

\(=5.16-16:4\)

\(=80-4\)

\(=76\)

Hok tốt

a, 24.64+36.24-100.24

=24.(64+36-1000

=24.0

=0

b, 5.4^2-16:2^2

=80-4

=76

a, 24 . 64 + 36 . 24 - 100 . 24

= 24 . ( 64 + 36 ) - 100

= 24 . ( 100 - 100 )

= 24 . 0

= 0

\(\frac{1}{9\cdot10}+\frac{2}{10\cdot12}+\frac{3}{12\cdot15}+\frac{4}{15\cdot19}+\frac{5}{19\cdot24}+\frac{6}{24\cdot30} \)
\(=\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{15}+\frac{1}{15}-\frac{1}{19}+\frac{1}{19}-\frac{1}{24}+\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{9}-\frac{1}{30}\)
\(=\frac{10}{90}-\frac{3}{90}\)
\(=\frac{7}{90}\)
 

24 . ( 16 - 5 ) - 16 . ( 24 - 5 )

= 24 . 16 - 24 . 5 - 16 . 24 - 16 . 5

= -24 . 5 - 16 . 5

= -40 . 5

= -200

24 . ( 16 - 5 ) - 16 . ( 24 - 5 )

= 24 . 16 - 24 . 5 - 16 . 24 - 16 . 5

= 24 . ( 16 - 5 ) - 16 . ( 24 - 5 )

= 24 . 11 - 16 . 21

= ( 24 - 16 ) . ( 11 - 21 )

= 8 . - 10

= - 80

24 . ( 16 - 5 ) - 16 . ( 24 - 5 )

= 24 . 16 - 24 . 5 - 16 . 24 + 16 .5

= 24 . ( 16 - 16) - 5 ( 24 -16 )

= 24 .      0       -  5 .   8

=     0              -      40

=         - 40