Question

三道简便计算题，一定要简便方法

Answer 1

3.16*238-116*1.38
=2*1.38*2*116-116*1.38
=4*1.38*116-1.38*116
=1.38*116(4-1)
=1.38*116*3
=1.38*348
=480.24

5.7*0.125-1/8+0.125*5.3
=5.7*0.125-0.125+0.125*5.3
=0.125*(5.7-1+5.3)
=0.125*(11-1)
=0.125*10
=1.25

3/2+7/6+13/12+21/20+31/30+43/42+57/56
=1+1/2+1+1/6+1+1/12+1+1/20+1+1/30+1+1/42+1+1/56
=7+1/2+1/6+1/12+1/20+1/30+1/42+1/56
=7+(60/120+20/120+10/120+40/120)+(4/168+3/168)
=7+94/120+7/168
=7+94/120+1/24
=7+94/120+5/120=7+(94+5)/120
=7+99/120
=7+33/40