How to make math.random return a decimal value between .1 and .3?

If I recall correctly, math.random only returns whole values.

math.random(10,30)/100)

The new Random feature supports floating point min/max values:

local random = Random.new()
local number = random:NextNumber(0.1, 0.3)

I'm aware that an answer has already been accepted, but I believe this to be the better solution because Random produces better random numbers than math.random currently, the syntax of Random.NextNumber is more intuitive, and the resulting random number will be more granular than dividing a random integer by 100 as in the previously accepted answer.

math.random has three modes:

• math.random(low, high) produces an integer between (inclusively) integers low and high
• math.random(high) is the same as math.random(1, high)
• math.random() produces a real number between 0 (inclusively) and 1 (exclusively).

You can "shrink" and "shift" the interval [0, 1) to become [.1, .3):

[0, 1) * 0.2 is [0, 0.2). [0, 0.2) + 0.1 is [0.1, 0.3).

In general, you can use the idiom low + (high - low) * math.random() to generate real numbers between low and high:

for i = 1, 10 do
    print(0.1 + 0.2 * math.random())
end

-- 0.26803754335269
-- 0.17887658532709
-- 0.25661984467879
-- 0.25968800662085
-- 0.28232947150245
-- 0.13951027384028
-- 0.16704455111176
-- 0.25364591889083
-- 0.15555494213477
-- 0.21079399110749