Maybe is case of large numbers you can compute digital root easier than the answer. For example, 25 * 26 = 650, digital root 2. Or take digital root of 25 and

Maybe is case of large numbers you can compute digital root easier than the answer. For example, 25 * 26 = 650, digital root 2. Or take digital root of 25 and 26 first, get 7 * 8 = 56, same digital root 2.