Gọi 1/4 số a là 0,25 . Ta có :

                   a . 3 - a . 0,25 = 147,07

                   a . (3 - 0,25) = 147,07 ( 1 số nhân 1 hiệu )

                      a . 2,75 = 147,07

                         a = 147,07 : 2,75

                          a = 53,48

TẦM NHƯ HƠI CĂNG

\(A=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2000}}{\frac{1999}{1}+\frac{1998}{2}+\frac{1997}{3}+....+\frac{1}{1999}}\)

\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+....+\frac{1}{2000}}{1+\left(\frac{1998}{2}+1\right)+\left(\frac{1997}{3}+1\right)+....+\left(\frac{1}{1999}+1\right)}\)

\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2000}}{\frac{2000}{2}+\frac{2000}{3}+\frac{2000}{4}+....+\frac{2000}{2000}}\)

\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2000}}{2000\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2000}\right)}\)

\(=\frac{1}{2000}\)

A = ( 1999 x 1998 + 1998 x 1997 ) x ( 1 + 1/2 : 3/2 - 4/3 )

A = ( 1999 x 1998 + 1998 x 1997 ) x ( 1 + 1/3 - 4/3 )

A = ( 1999 x 1998 + 1998 x 1997 ) x [ 1 + ( -1 ) ]  

A = ( 1999 x 1998 + 1998 x 1997 ) x 0

A = 0

b) \(\frac{1}{1000}+\frac{13}{1000}+\frac{25}{1000}+...+\frac{87}{1000}+\frac{99}{1000}\)

\(=\frac{1+13+25+...+85+97}{1000}=\frac{\left(97+1\right).\left[\left(97-1\right):12+1\right]:2}{1000}\)

\(=\frac{49.9}{1000}=\frac{441}{1000}.\) ( Đề bài sai nhé bạn tử số : 1; 13; 25; 37; 49 ; 61; 73; 85 ; 97. )

Câu c:B = (1999x1998 + 1998x1997)x(1+1/2: 1 1/2 - 11/3)

B = (1999x1998 + 1998x1997)x(1+1/2:3/2-4/3)

B = (1999x1998 +1998 x1997) x (1+1/2x2/3 - 4/3)

B = (1999 x 1998 + 1998 x 1997) x(1+1/3 - 4/3)

B = (1999 x 1998 + 1998 x 1997) x (4/3 - 4/3)

B = (1999 x 1998 + 1998 x 1997) x 0

B = 0

a,(2016 + 2).1008:2=1017072

b,(2001+5).500:2=501500

c,

501 500