come in handy:to be useful when needed 有用处,派上用场,需要时可资利用

The extra money came in very handy.
这笔额外的钱正好派上了用场.

Don't throw that away─it might come in handy.
别把它扔了---它或许有用.

The money my aunt gave me will come in handy to pay for my music lessons.
姨妈给我的钱正好付音乐课的学费.

handy就是有用的意思.
Handy is a very handy word.

go a long way towards doing something:to help very much in achieving something (对做某事)帮助很大,作用很大
The new law goes a long way towards solving the problem.
新的法律十分有助于解决这一问题.