What is the largest number that will divide both 14 and 28 perfectly, with no remainder?

• A. 7
• B. 21
• C. 28
• D. 14

Answer: (D)

The largest number that divides both numbers without a remainder is found by the greatest common divisor. For 14 and 28, the common factors are 1, 2, 7, and 14. The biggest of these is 14, and 28 isn’t a divisor of 14, so it can’t be the common divisor either. You can also see this from prime factors: 14 = 2 × 7 and 28 = 2² × 7, so the shared part is 2 × 7 = 14. Therefore, 14 is the largest common divisor.