Can anyone told me how can i do this math function?

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1

Hello there, Im trying to make a function that give me the largest number of multiples of the first number (x), and it must be less than the second number(y) for positive numbers and more for negative numbers

exemples:


x = 10
y = 31

--> Output: 30

x = 4
y = 15.2

--> Output: 12

x = -0.5
y = -10.56

--> Output: -10.5

x = 7
y = 12

--> Output: 7

any idea how can I do it, Sorry guys I’m really a math failer

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2

All numbers have an infinite number of multiples so uh I don’t understand what your trying to do.

3

You could do something like this:

function goesInto(x, y)
	return x*math.floor(y/x)
end

The -0.5 example wouldn’t produce that result because it isn’t a positive integer.

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4

i tould you the multiple should be less than the second number y

x = 3
y = 10

So the largest multiple less than 10 of 3 is 9
the function return 9

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5

You would just divide y by x, take the first number without the decimals, and multiply x by that number. I assume you want whole numbers, if so that’s all you need to do.

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6

Can’t you just take the remainder of the number and subtract it from the number itself?

local x = 10
local y = 31
print(y - (y % x)) --Outputs 30
4 Likes
7

Yep this should and could be marked as one of the possible the answer (there might be a lot more like @BenMactavsin but I haven’t tested it with all examples). I also came up with the same thing. But here is a list of outputs with the given examples which shows it’s close enough (especially with the -0.5,-10.56 case).

The same function 
local function largestMultipleOfNum1(num1,num2)
    return math.floor(num2/num1)*num1
end

print(largestMultiple(10,31))
print(largestMultiple(4,15.2))
print(largestMultiple(-0.5,-10.56))
print(largestMultiple(7,12))

Output:

30
12
-10.5
7
3 Likes
8

Ok but how can i make it work even with the negative float numbers? is that possible?
like -0.8, 0.1…

9

I mean you could make it work, in a way:

local x = 0.3
local y = -4
print(y - (math.sign(y) * (math.abs(y) % math.abs(x)))) --Outputs -3.9
10

This works:

function goesInto(x, y)
	local result = x*math.floor(y/x)
	if result > 0 then
		return math.floor(result)
	else
		return math.ceil(result)
	end
end
11

wouldn’t @BenMactavsin’s solution work fine?

it looks a lot more simple then some other answers

12

You’re not! Nobody was born with the ability to do math, don’t worry about it. If you really want to learn math, you can get there with practice.

Anyway, here’s what I would do:

local function largestMultiple(x, y)
	return math.floor(y / x) * x
end

I don’t want to just spoonfeed code, so I’ll explain what this does:

Key knowledge - math.floor

math.floor rounds numbers down. This means math.floor(4.8) will return 4, math.floor(8.3) will return 8, and math.floor(65.9) will return 65.

With that out of the way, let’s break the function down to be even more simple.

local function largestMultiple(x, y)
    local div = y / x
    local roundedDown = math.floor(div)

	return roundedDown * x
end

If you called the function with (10, 31), this would happen:

local function largestMultiple(x, y)
	-- x = 10, y = 31
	
	local div = y / x -- This is equal to 3.1 (31 / 10)
	local roundedDown = math.floor(div) -- We are rounding it down, so this is now equal to 3
	
	return roundedDown * x -- We're multiplying 3 by x (10), so now we return 30!
end

I hope you find this to be helpful :smile:

2 Likes
13

I tried to do that, but it doesn’t work with x = -0.5 and y = -10.56

Edit:
@PerilousPanther found a workaround in this post: Can anyone told me how can i do this math function? - #10 by PerilousPanther

But it is quite a long function, and probably inefficient (might be harmful if used in a high-frequency loop/event like RenderStepped)

14

Because the largest number that is smaller* than -10.56 that can be divided by -0.5 with the remainder of 0 is -10.5, not -10.

*Note: The actual answer is -11 since -11 is smaller than -10.56 but for the purposes of this post made by OP, it’s -10.5.
Another point is is that OP never specified that answer needs to be an integer so there is no reason for the answer to be -10.

1 Like
15

@BenMactavsin function work for me good
thanks a lot for eveyone try to help :smile:

1 Like
16

Yes i do it worng sorry about that i tould you im a math failer

17

stop putting yourself down, you aren’t a failer at all!

1 Like
18

@D0RYU @TheHeckingDev Thanks so much for accusing me both of you, but really i dont understand math that much i knew every single math function in roblox but i dont know how to use them to make this function

1 Like