/**
 * Calculates the final gravity as specific gravity using the estimated yest
 * attenuation and the original (specific) gravity.
 * @param {number} originalGravity Starting specific gravity.(e.x. 1.051)
 * @param {number} attenuation estimated yeast attenuation (e.x. 75%)
 * @returns {number} final gravity as specific gravity
 */
export default function finalGravity(originalGravity: number, attenuation: number): number;