3倍根号40分之根号5
=3×√5/√40
=3×√(5/40)
=3×√(1/8)
=3√(2/16)
=3×√2/√16
=3×(√2)/4
=(3√2)/4
根号27乘根号50除以根号6
=√27×√50÷√6
=√(27×50÷6)
=√225
=15