(1)√12×√18×√27
=2√3×3√2×3√3
=54√2
（2）√（-3）²×16×25
=√3²×4²×5²
=3×4×5
=60
（3）√0.16×0.25×400
=√0.4²×0.5²×20²
=0.4×0.5×20
=4