How about three quarters by two nines plus 0.75 by five nines

How about three quarters by two nines plus 0.75 by five nines


3/4×2/9+0.75×5/9
=3/4×2/9+3/4×5/9
=3/4×﹙2/9+5/9﹚
=3/4×7/9
=7/12



How to calculate 85 out of 86 × 1
fast


86 × (1 / 85)
86×1/85
=(85+1)×1/85
=1+1/85
=1 and 1 / 85



86 times 4 / 85


86*4/85 =(85+1)*4/85 =85*4/85+1*4/85 =4+4/85
=4 / 85 is not so simple. It's just a distribution law