如何使用Lua for Corona SDK随机生成数字

我有一个简单的游戏，可以从中产生数学问题，但是效率很低，因为我必须自己亲自解决所有问题。

有谁比这更好地了解一些代码，或者将我引向一篇很好的教程，介绍如何进行设置？谢谢你。

local M = {}

M["times"] = {
    {
        question="6 x 5",  --The question.
        answers={"30", "11", "29", "20"},  --Array of possible answers.
        answer=1   --Which one from the above array is the correct answer.
    },
}

return M

更新：

{
    a = math.random( 1, 20 ),
    b = math.random( 1, 20 ),
    question = a * b,
    answer = math.random( m, n )
}

我以为这可以用，但是我在控制台中收到此错误：

mathQuestions.lua:55: attempt to perform arithmetic on global 'a' (a nil value)

更新＃2

--mathQuestions.lua
M["times"] = {

    local rnd = function (x) return math.random(1,x) end
    M.times = {}
    local numQuestions = 10 -- how many questions in your database
    for i=1,numQuestions do
        local obj =
        {
            left=math.random(1,10),
            right=math.random(1,10),
            answers={rnd(100), rnd(100), rnd(100), rnd(100)},
            answerIndex=rnd(4) -- will override answer[answerIndex] later
        }
        obj.answer = obj.left * obj.right
        obj.answers[obj.answerIndex] = obj.answer
        M.times[i] = obj
    end

}

我收到此错误：

ERROR: Failed to execute new ( params ) function on 'game'

mathQuestions.lua:121: unexpected symbol near 'local'