Q199
ArithmeticNumber Series & Progressions
What is the missing number? 32, 19, 8, ?
- a.3
- b.12
- c.5
- d.1
Answer: (D) 1
The numbers decrease by successive prime numbers taken in descending order: $32-13=19$, $19-11=8$, and the next prime below 11 is 7, so $8-7=1$. Hence the missing number is 1. The differences are not simply decreasing odd numbers (13, 11, 9), which would give $-1$, a value not among the options; of the choices, only 1 fits a consistent rule. Tip: when the differences are 13 and 11, test primes as well as odd numbers.