41/54

41/54

3/4+3= 3/4+12/4=15/4

5/2 x 4 =5 x 4/2 = 20/2 = 10

2-7/8=16/8-7/8=9/8

9/4-2=9/4-8/4=1/4

5: 5/7=5 x 7/5= 35/5=7

5/6:2/7=5/6 x 7/2 = 35/12

1/6+2/3 x 8/9= 1/6+ 16/18= 3/18+16/18=19/18

1/6 + 2/3 : 4/5 = 1/6+ 2/3 x 5/4= 1/6+5/6=6/6=1

                đúng cho mình nhé

Ta có: \(1+3+6+10+\cdots+45+55\)

\(=\frac12\times\left(2+6+12+20+\cdots+90+110\right)\)

\(=\frac12\times\left(1\times2+2\times3+\cdots+9\times10+10\times11\right)\)

\(=\frac12\times\left\lbrack1\times\left(1+1\right)+2\times\left(2+1\right)+\cdots+10\times\left(10+1\right)\right\rbrack\)

\(=\frac12\times\left\lbrack\left(1\times1+2\times2+\cdots+10\times10\right)+\left(1+2+\cdots+10\right)\right\rbrack\)

\(=\frac12\times\left\lbrack10\times\left(10+1\right)\times\frac{\left(2\times10+1\right)}{6}+10\times\frac{11}{2}\right\rbrack\)

\(=\frac12\times\left\lbrack10\times11\times\frac{21}{6}+5\times11\right\rbrack=\frac12\times\left\lbrack5\times11\times7+5\times11\right\rbrack\)

\(=\frac12\times5\times11\times\left(7+1\right)=\frac{55}{2}\times8=55\times4=220\)

Ta có: \(1\times10+9\times2+\cdots+10\times1\)

\(=2\times\left(1\times10+2\times9+3\times8+4\times7+5\times6\right)\)

\(=2\times\left\lbrack1\times\left(11-1\right)+2\times\left(11-2\right)+3\times\left(11-3\right)+4\times\left(11-4\right)+5\times\left(11-5\right)\right\rbrack\)

\(=2\times\left\lbrack11\times\left(1+2+3+4+5\right)-\left(1\times1+2\times2+3\times3+4\times4+5\times5\right)\right\rbrack\)

\(=2\times\left\lbrack11\times15-\left(1+4+9+16+25\right)\right\rbrack\)

=2x(165-55)

=2x110

=220

Ta có: \(\frac{1\times10+9\times2+\cdots+10\times1}{1+3+6+10+\cdots+45+55}\)

\(=\frac{220}{220}\)

=1

a) 3 x 8 - 16 = 24-16

                    = 8

b ) 5 x 10 + 40 = 50 + 40

                        = 90

c ) 4 x 2 + 92 = 8 + 92

                      = 100

Tk nha ( chúc bạn học giỏi )

a)3x8-16=24-16

           =8

b)5x10+40=50+40

                 =90

c)4x2+92=8+92

               =100

Em nên gõ công thức trực quan để đề bài rõ ràng nhé