7.2*58+0.72*42这题如何简便运算十分急

7.2*58+0.72*42
=7.2*58+7.2*42*1/10
=7.2（58+42）*1/10
=7.2*100*1/10
=72

=7.2*58+0.72*(4.2*10)
=7.2*58+(0.72*10)*4.2
=7.2*5.8+7.2*4.2
=7.2*(5.8+4.2)
=7.2*10
=72

7.2*58+0.72*42
=7.2*58+0.72*(4.2*10)
=7.2*58+(0.72*10)*4.2
=7.2*5.8+7.2*4.2
=7.2*(5.8+4.2)
=7.2*10
=72