How do I make a leaderstat multiply a leaderstat?

What I would do is insert a separate value in the player that indicates how much the multiplier is.

game.Players.PlayerAdded:Connect(function(plr)
local multi = Instance.new("IntValue",plr)
multi.Name = "Multiplier"
local leaderstats = Instance.new("Folder",plr)
leaderstats.Name = "leaderstats"
local Cash = Instance.new("IntValue",leaderstats)
Cash.Name = "Cash"
multi.Value = 2 -- lets say the multiplier is * 2
end)

the script above simply inserts the values needed into the player.

--seperate script
game.Players.PlayerAdded:Connect(function(plr)
while true do
plr.leaderstats.Cash.Value = plr.leaderstats.Cash.Value + plr.Multiplier.Value * 10 --really just 2*10
wait(120)
end
end)

not checked, please reply if you see any errors. thank you!