Nine is usually thought of as a lucky number because it is the product of three times three.

9通常被认为是一个幸运数字，因为它是3乘以3的乘积。

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Over the course of a school year, each of Eagle County's 470 teachers is evaluated three times and is observed in class at least nine times by master teachers, their principal and peers called mentor teachers.

WSJ: Bill Gates on the Importance of Measurement

Climate experts have argued that we ought to stop emitting greenhouse gases within fifty years, but by then the demand for energy could easily be three times what it is today: nine cubic miles of oil.

NEWYORKER: The Climate Fixers

Appiah has scored seven times in his last three matches, and nine in nine appearances since joining from Peterborough United and is pleased to be impressing.

BBC: Appiah leads Linnets goal drive