BigInteger x ratio or percent

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Test_BigInteger : MonoBehaviour
{
    public System.Numerics.BigInteger m_Damage = 1000000000000000; // 10000000000000000000
    public float m_Ratio = 1.1f;

    // Start is called before the first frame update
    void Start()
    {
        CalcR(m_Damage, m_Ratio);
        CalcR(100, m_Ratio);
        CalcR(60000000, m_Ratio);
        CalcR(3422346435, m_Ratio);

        CalcP(10000000000000000000, 10);
        CalcP(100, 10);
        CalcP(60000000000, 10);
        CalcP(82387234823, 100);
    }

    System.Numerics.BigInteger CalcR(System.Numerics.BigInteger value, float ratio)
    {
        System.Numerics.BigInteger ratio1000 = Mathf.RoundToInt(ratio * 1000);
        System.Numerics.BigInteger value1000 = value * ratio1000;

        var rst = value1000 / 1000;

        Debug.Log($"{value:#,###} x {ratio} = {rst:#,###}");

        return rst;
    }

    System.Numerics.BigInteger CalcP(System.Numerics.BigInteger value, System.Numerics.BigInteger per)
    {
        Debug.Log($"{value:#,###} + {per}% = {value + (value / 100 * per):#,###}");

        return value + (value / 100 * per);
    }
}