28×5+2×3×35+21×20+14×40+8×62 55×66+66×77+77×88+88×99脱式计算

楼上~ 有点小问题
28×5+2×3×35+21×20+14×40+8×62
=28×5+6×35+21×20+14×40+8×62
=140+210+210+560+496
=1826
55×66+66×77+77×88+88×99
=11×5×11×6+11×6×11×7+11×7×11×8+11×8×11×9
=11×11×(5×6+6×7+7×8+8×9)
=121×(30+42+56+72)
=121×200
=24200

28×5+2×4×35+21×20+14×40+8×62 =2×2×7×5+2×4×5×7+3×7×4×5+2×7×5×2×4+8×62=2×2×7×5×（1+2+3+4）+496 =10×14×10+496 =1400+496 =1896 55×66+66×77+77×88+88×99=11×5×11×6+11×6×11...