Answer:3/8
Explanation:
The simplest form of 
15 /40 is 3 /8 . 
 
Steps to simplifying fractions 
Find the GCD (or HCF) of numerator and denominator 
GCD of 15 and 40 is 5 
Divide both the numerator and denominator by the GCD 
15 ÷ 5 
40 ÷ 5 
Reduced fraction: 
3 /8 
 
Therefore, 15/40 simplified to lowest terms is 3/8.