Question

287×102-2×287如何简便运算？

Answer 1

287×102-2×287
=287×(102-2)
=287×100
=28700

Answer 2

乘法分配律为：两个数的和与一个数相乘，先将它们与这个数分别相乘，再相加，积不变．即：（a+b）×c=a×c+b×c．反过来则：a×c+b×c=（a+b）×c
287×102-2×287
= 287× ( 102-2）
= 287×100
= 28700