巧算 25×125×4×8 27×99+27 38×101 300÷25 125×16 864÷(27-23)×12.
(1)25×125×4×8, =(25×4)×(125×8), =100×1000, =100000; (2)27×99+27, =27×(99+1), =27×100, =2700; (3)38×101, =38×100+38×1, =3800+38, =3838; (4)300÷25, =(300×4)÷(25×4), =1200÷100, =12; (5)125×16, =125×8×2, =1000×2, =2000; (6)864÷(27-23)×12, =864÷4×12, =216×12, =2592. |