Question

Tính nhanh 

a) 55 + 60 + 45 + 30 + 40 + 70

b) 4 + 20 + 6 + 80 

Answer 1

\(55+60+45+30+40+70\)

\(=\left(55+45\right)+\left(60+40\right)+\left(30+70\right)\)

\(=100+100+100=300\)

\(4+20+6+80=\left(4+6\right)+\left(20+80\right)=10+100=110\)

Answer 2

a) \(55+60+45+30+40+70\)

\(=\left(55+45\right)+\left(60+40\right)+\left(30+70\right)\)

\(=100+100+100\)

\(=100.3=300\)

b) \(4+20+6+80\)

\(=\left(4+6\right)+\left(20+80\right)\)

\(=10+100=110\)

Answer 3

=300

= 110

Answer 4

a) 55 + 60 + 45 + 30 + 40 + 70

= ( 45 + 55 ) + ( 60 + 40 ) + ( 30 + 70 )

=      100      +       100      +      100

=                           300

b) 4 + 20 + 6 + 80 

= ( 4 + 6 ) + ( 20 + 80 )

=     10     +     100

=           110

Answer 5

a,=(55+45)+(60+40)+(70+30)=100

b,=(4+6)=(20+80)=110

Answer 6

\(a.55+60+45+30+40+70=\left(55+45\right)+\left(60+40\right)+\left(30+70\right)\)\(70\))

\(=100+100+100\)

\(=100x3=300\)

\(b.4+20+6+80\)\(=\left(4+6\right)+\left(80+20\right)\)

\(=10+100=110\)