Question

bài 1,tính nhanh 

a, 41x36+59x90+41x84+59x30

b, 4x51x7+2x86x7+12x2x7.

bài 2:tính tổng sau bằng cách nhanh nhất

a, 87+35+13

b,62+34+66 

c, 212+109+188

d,305+195+110

e,15+46+85+54

g,277+144+86+123

Answer 1

\(41\times36+59\times90+41\times84+59\times30=41\times\left(36+84\right)+59\times\left(90+30\right)=41\times120+59\times120=120\times\left(41+59\right)=120\times100=12000\)

\(4\times51\times7+2\times86\times7+12\times2\times7=4\times7\times\left(51+43+6\right)=28\times100=2800\)

\(87+35+13=100+35=135\)

\(62+34+66=62+100=162\)

\(212+109+188=400+109=509\)

\(305+195+110=500+110=610\)

\(15+46+85+54=100+100=200\)

\(277+144+86+123=400+230=630\)