677 + 969 + 123 = 677 + 123 + 969 = 1769

  7h15p+4h45p+1h28p

=12h+1h28p

=13h28p

lấy 7 h 15 + 4h 45=11h 60p=12h

12h + 1h 28p=13h 28p

325+6,8+675+3,2=(6,8+3,2)+675+325

                             =10+1000

39/17

39/17

\(0,127\times3+0,127\times6+0,127\)

\(=0,127\times3+0,127\times6+0,127\times1\)

\(=0,127\times\left(3+6+1\right)\)

\(=0,127\times10\)

\(=1,27\)

= 0,127 x 3 + 0,127 x 6 + 0,127

= 0,127 x ( 3 + 6 + 1 )

= 0,127 x 10

= 1,27

  2,15 x 23,06 + 2,15 x 76,94 + 17,85

=2,15 x ( 23,06 + 76,94 ) + 17,85

=2,15 x 100 + 17,85

=215 + 17,85

=232,85

2.15 * 23.06 + 2.15 * 76.94 + 17.85

2.15 *[23.06+76.94+17.85]

2.15 *117.85

253.3775

\(A=\frac{1}{4}+\frac{1}{16}+\frac{1}{64}+...+\frac{1}{16384}\)

\(A=\frac{1}{2^2}+\frac{1}{2^4}+...+\frac{1}{2^{14}}\)

\(2^2A=1+\frac{1}{2^2}+...+\frac{1}{2^{12}}\)

\(4A-A=\left(1+\frac{1}{2^2}+...+\frac{1}{2^{12}}\right)-\left(\frac{1}{2^2}+\frac{1}{2^4}+...+\frac{1}{2^{14}}\right)\)

\(3A=1-\frac{1}{2^{14}}\)

\(A=\frac{1-\frac{1}{2^{14}}}{3}\)

mình cũng đang phân vân câu này

\(38\times8+27\times2\)

\(=\left(38\times8\right)+\left(27\times2\right)\)

\(=304+54\)

\(=358\)

$38\times 8+27\times 2$

$=\left(38\times 8\right)+\left(27\times 2\right)$

$=304+54$

$=358$