40 is not divisible by 7, while 21, 28, and 35 are all multiples of 7.

A number is divisible by 8 if the number formed by its last three digits is divisible by 8. 90 is not divisible by 8.

A number is divisible by 9 if the sum of its digits is divisible by 9. The sum of the digits of 50 (5 + 0 = 5) is not divisible by 9.

In decimal, '54' = 32, '45' = 29, '63' = 39, '36' = 22. '63' is the largest.

'72' in base-8 is 58 in decimal, which is larger than the others.

The binary system is the most commonly used in digital electronics due to its two-state nature.

The Roman numeral system is not positional, as it does not use place value to determine the value of digits.

All pairs have the same remainder when divided by 6: 8 mod 6 = 2, 14 mod 6 = 2; 10 mod 6 = 4, 16 mod 6 = 4; 12 mod 6 = 0, 18 mod 6 = 0.

15 and 28 have no common factors other than 1, making their GCD equal to 1.

15 and 28 are coprime, meaning their GCD is 1.

The LCM of 4 and 9 is 36.

The HCF of 15 and 28 is 1, making them coprime.

The HCF of 12 and 18 is 6, as both numbers are divisible by 6, while the other pairs have higher HCFs.

The GCF of 15 and 28 is 1, making them coprime, while the other pairs share common factors.

Base 8 (octal) is not more efficient than base 2 (binary); it simply represents values in a different way.

A number can have an infinite number of multiples, as you can keep adding the number to itself indefinitely.

A factor of a number is always less than or equal to that number, making the last statement incorrect.

Every number has at least two factors: 1 and the number itself, but some numbers can have more than two factors.

All statements are true regarding multiples.

Base-2 can represent all integers, as it is a complete positional system.

Different numeral systems can represent the same value, such as the decimal 10 and binary 1010.

Base-2 (binary) is not used in human languages; it is primarily used in computing.

The statement that the decimal system is the only system used in mathematics is incorrect; other systems like binary and hexadecimal are also used.

30 is a multiple of 5, as it can be expressed as 5 multiplied by 6.

The passage suggests that digital sum will evolve and integrate with emerging technologies, indicating a promising future.

The passage suggests that a solid understanding of digital sum is essential for effective data analysis in various fields.

All statements are true; multiples can be negative, can be equal to the number, and are always integers.

By definition, a factor divides the number evenly, leaving no remainder.

The sum of two multiples of 3 is always a multiple of 3, as multiples of a number are closed under addition.

The smallest factor of any number is always 1, as 1 divides every integer.