九百九十九乘七分之五加六百六十六乘七分之二能用简便算法吗?

Answer 1

(1000-1)*(5/7+2/7*2/3) = (1000-1)*(15+4)/21 = (1000-1)*19/21 = (19000-19)/21 = 18981/21 = 6327/7

Answer 2

能，如图