To reduce 4/10 to the lowest terms, which number do you divide both numerator and denominator by?

• A. Two
• B. Three
• C. Four
• D. Five

Answer: (A)

Reducing a fraction to its lowest terms means dividing the top and bottom by their greatest common factor. For 4/10, both numbers share the factor two. Dividing numerator and denominator by two gives 4 ÷ 2 = 2 and 10 ÷ 2 = 5, so the fraction becomes 2/5. This is already in lowest terms because 2 and 5 have no common factors besides 1. Other divisors don’t work because three doesn’t divide either 4 or 10, four divides 4 but not 10, and five divides 10 but not 4.