1. 2,4 x 1994 x 2 + 1,6 x 3996 x 3 + 1,2 x 4010 x 4

= ( 2,4 x 1994 x 2 ) + ( 1,6 x 3996 x 3 ) + ( 1,2 x 4010 x 4 )

= ( 2,4 x 2 x 1994 ) + ( 1,6 x 3 x 3996 ) + ( 1,2 x 4 x 4010 )

=       4,8 x 1994     +        4,8 x 3996   +       4,8 x 4010

=      4,8 x ( 1994 + 3996 + 4010 )

=      4,8 x           10 000

=               48000

2. 3 + 7 + 11 + 15 +........+ 95 + 99 - 275

= [ ( 99 - 3 ) : 4 + 1 ] - 275

=    25             - 275

= [ ( 99 + 3 ) x 25 : 2 ] - 275

=       1275                 - 275

=                  1000

kick mình nhé bạn

1/48000

2/chịu

mik cũng có câu hỏi như thế này ,các bn giải thik giúp mik đc ko

\(\frac{2,4\times1994\times2+1,6\times3996\times3+1,2\times4010\times4}{3+7+11+...+95+99-275}\)

\(=\frac{0,2\times6\times2\times2\times997\times2+0,2\times8\times6\times666\times3+0,2\times6\times2\times2005\times4}{\left(99+3\right)\times49:2-275}\)

\(=\frac{0,2\times6\times8\times997+0,2\times8\times6\times666\times3+0,2\times6\times8\times2005}{2499-275}\)

\(=\frac{0,2\times6\times8\times\left(997+666\times3+2005\right)}{2224}\)

\(=\frac{0,2\times2\times3\times8\times\left(997+1998+2005\right)}{8\times2\times0,2\times695}\)

\(=\frac{3\times\left(2995+2005\right)}{695}\)

\(=\frac{3\times5000}{695}=\frac{3\times1000\times5}{5\times139}\)

\(=\frac{3\times1000}{139}=\frac{3000}{139}\)

=???????????

tinh nhanh 2 bai nay giup mk di ma cac ban oi

tìm x 275% : x - 3/4 : x + 1,2  : x = 1,6                                                       giúp mik với, ai làm đg mik tick ng đó!!!

a=1/3+1/99=34/99

Ta có: \(A=\frac{1}{3}.\frac{1}{7}+\frac{1}{7}.\frac{1}{11}+\frac{1}{11}.\frac{1}{15}+...+\frac{1}{95}.\frac{1}{99}\)

              \(=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+.....+\frac{1}{95}-\frac{1}{99}\right)\)

               \(=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{99}\right)\)

                \(=\frac{1}{4}.\frac{32}{99}=\frac{8}{99}\)

A = 1/4 x (1/3-1/7+1/7-1/11+1/11-1/15+..........+1/95-1/99)

= 1/4 x(1/3-1/99)

= 1/4 x 32/99

= 8/99

\(4A=\frac{4}{3.7}+...+\frac{4}{95.99}\)

\(4A=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{95}-\frac{1}{99}\)

\(4A=\frac{1}{3}-\frac{1}{99}=\frac{32}{99}\)

\(\Rightarrow A=\frac{8}{99}\)

\(A=\frac{1}{3.7}+\frac{1}{7.11}+...+\frac{1}{95.99}\)

\(A=\frac{1}{4}.\left(\frac{4}{3.7}+\frac{4}{7.11}+...+\frac{4}{95.99}\right)\)

\(A=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{95}-\frac{1}{99}\right)\)

\(A=\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{99}\right)\)

\(A=\frac{1}{4}.\frac{32}{99}\)

\(A=\frac{8}{99}\)

\(A=\frac{1}{3}.\frac{1}{7}+\frac{1}{7}.\frac{1}{11}+\frac{1}{11}.\frac{1}{15}+...+\frac{1}{95}.\frac{1}{99}.\)

    \(=\frac{1}{3.7}+\frac{1}{7.11}+\frac{1}{11.15}+...+\frac{1}{95.99}\)

\(4A=\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+...+\frac{4}{95.99}\)

\(4A=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{95}-\frac{1}{99}\)

\(4A=\frac{1}{3}-\frac{1}{99}\)\(=\frac{33-1}{99}\)\(=\frac{32}{99}\)

\(\Rightarrow A=\frac{32}{99}:4=\frac{32}{99}.\frac{1}{4}=\frac{8}{99}\)