6乘0.99加0.06
=6*0.09+0.06
=9*0.06+0.06
=(9+1)*0.06
=10*0.06
=0.6
20分之19乘21
=19*21/20
=(20-1)*(20+1)/21
=(400-1)/21
= 399/20
=19.95
73.75减(8.75减4.3
=73.75-(8.75-4.3)
=73.75-8.75+4.3
=65+4.3
=69.5
0.625乘7又2分之1
=(5/8)*[8-(1/2)]
=5-(5/8/2)
=5-0.3125
=4.6875