25/2

181/5

247/2

71/5

a)`1,25 + 1,25 xx 2 + 7 xx 1,25=1,25 xx (1+2+7) = 1,25 xx 10 =12,5`

b)`3,62xx12–2xx0,362xx10=3,62 xx 12 -2 xx 3,62=3,62xx(12-2)=3,62xx10=36,2`

c)`12,35xx15–1,235xx10xx6+12,35=12,35xx15–12,35xx6+12,35=12,35xx(15-6+1)=12,35xx10=123,5`    

d)`1,42 : 0,5 + 1,42 xx 8=1,42xx2+1,42xx8=1,42xx(2+8)=1,42xx10=14,2`

Tính bằng cách thuận tiện nhất:

a) 1,25 x 3,6 + 2,5 x 7,2 x 5 -1,25 x 8

= 1,25 x 4 x 0,9 + 2,5 x 2 x 3,6 x 5 - 1,25 x 4 x 2

= 5 x 0,9 + 5 x 18 - 5 x 2 

= 4,5 + 90 - 10

= 84,5

b) 4,16 x 4/5 -80% x 0,16 + 0,96: 1,2

= 4,16 x 0,8 - 0,8 x 0,16 + 0,8

= 0,8 x (4,16 - 0,16 + 1)

= 0,8 x 5 = 4

\(a.1,25\times5\times6,3\div0,125\times2\\ =\left(5\times2\right)\times\left(1,25\div0,125\right)\times6,3\\ =10\times10\times6,3=630\)

\(b.12,5\times6,9+0,1\times6,9\times865\times6,9\\ =6,9\times\left(12,5+86,5+1\right)\\ =6,9\times100=690\)

a, \(=16,24\left(12-3+1\right)\)

\(=16,24.10=162,4\)

b, \(=1,25\left(1+2+7\right)\)

\(=1,25.10=12,5\)

c, \(=2,46\left(2+8\right)\)

\(=2,46.10=24,6\)

\(a,=16,24\times12-16,24\times3+16,24\times1\\ =16,24\times\left(12-3+1\right)=16,24\times10=162,4\\ b,=1,25\times\left(1+2+7\right)=1,25\times10=12,5\)

a 16.24( 12-10+3)=16.24 x 5=81.2

b  1.25(1+2+7)=1.25 x 10= 12.5

c  2.46 x 2 + 2.46 x8 = 2.46(2 + 8)=2.46 x 10=24.6

\(1,25:0,5+1,25\times8\\ =1,25\times2+1,25\times8\\ =1,25\times\left(2+8\right)\\ =1,25\times10\\ =12,5\)

\(1,25+2.1,25+1,25.3\)

\(=1,25.\left(1+2+3\right)\)

\(=1,25.6\)

\(=7,5\)

\(1,25+2.1,25+1,25.3\)

\(=1,25.\left(1+2+3\right)\)

\(=1,25.6\)

\(=7,5\)

1,25 + 2 x 1,25 + 1,25 x 3

= 1,25 x (1 + 2 + 3)

= 1,25 x 6

= 7,5

13,5+1,25x7-12,25

=13,5-12,25+1,25x7

=1,25x(1+7)

=1,25x8

=10