Question

Tính nhanh :

a) 168 x 168 - 168 x 68

b) 201,5 x 17 - 2015 x 16 - 201,5

c) 1,5 + 1,5 x 2 + 1,5 x 7 -10

d) 1,25 x 2,5 x 64

Answer 1

a. 168x168-168x68

= 168x(168-68)

= 168x100

= 16800

b. 201,5x17-2015x16-201,5

= 201,5x17-201,5x160-201,5

= 201,5x(17-16-1)

= 201,5x0

= 0

c. 1,5 + 1,5x2+1,5x7-10

= 1,5x1+1,5x2+1,5x7-10

= 1,5x(1+2+7)-10

= 1,5x10-10

= 10x(1,5-1)

= 10x0,5

= 5

d. 1,25x2,5x64

= 1,25x64x2,5

=80x2,5

= 200

Answer 2

a)168*168-168*68=168*(168-68)=168*100=16 800

b)201,5*17-2015*16-201,5=201,5*17-201,5*160-201,5=201,5*(17-160-1)=201,5*(-144)=-29016

c)1,5+1,5*2+1,5*7-10=1,5*(1+2+7)-10=1,5*10-10=(1,5-1)*10=0,5*10=5

d)1,25*2,5*64=1,25*2,5*8*8=(1,25*8)*(2,5*8)=10*20=200