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1. Three integers have exactly three positive divisors. Which is the odd one out?
- A. 49
- B. 121
- C. 143 (answer)
- D. 169
49, 121 and 169 are prime squares with three divisors. 143 = 11 × 13 has four: 1, 11, 13 and 143.
2. Three fractions have terminating decimal expansions. Which is the odd one out?
- A. 7/40
- B. 11/24 (answer)
- C. 13/80
- D. 17/125
A reduced fraction terminates in base ten only if its denominator has no prime factors except 2 and 5. 24 contains 3.
3. Three words contain a, e, i, o and u exactly once each. Which is the odd one out?
- A. Educational (answer)
- B. Sequoia
- C. Facetious
- D. Abstemious
Educational contains a twice. The other three words contain each of the five standard vowel letters exactly once.
4. Three words become a different common English word when reversed. Which is the odd one out?
- A. Drawer
- B. Stressed
- C. Window (answer)
- D. Reward
Drawer reverses to reward, stressed to desserts and reward to drawer. Window reverses to wodniw.
5. Three are triangular numbers, formed by adding 1 + 2 + ... + n. Which is the odd one out?
- A. 36
- B. 45
- C. 55
- D. 65 (answer)
36, 45 and 55 are sums through 8, 9 and 10. The next triangular number is 66, not 65.
6. Three lengths can be a right triangle's hypotenuse with positive whole-number legs. Which is the odd one out?
- A. 13
- B. 19 (answer)
- C. 25
- D. 17
5-12-13, 7-24-25 and 8-15-17 are Pythagorean triples. No two positive integer squares sum to 19 squared.
7. Three words have letters in alphabetical order, allowing repeats. Which is the odd one out?
- A. Almost
- B. Chintz
- C. Effort
- D. Being (answer)
Almost, chintz and effort have non-decreasing alphabetical order. Being ends in g after n, breaking the order.
8. Three integers leave remainder 1 when divided by 8. Which is the odd one out?
- A. 121
- B. 145
- C. 171 (answer)
- D. 193
121, 145 and 193 are one more than a multiple of 8. 171 = 8 × 21 + 3.
9. Three words alternate consonant and vowel letters throughout. Only a, e, i, o and u count as vowels. Which is the odd one out?
- A. Banana
- B. Potato
- C. Tomato
- D. Carrot (answer)
Banana, potato and tomato alternate consonants and vowels. Carrot contains adjacent consonants.
10. Three integers equal the sum of the cubes of their decimal digits. Which is the odd one out?
- A. 153
- B. 370
- C. 371
- D. 372 (answer)
153 = 1 + 125 + 27, 370 = 27 + 343, and 371 = 27 + 343 + 1. The digit cubes of 372 sum to 378.
11. Three words contain exactly three e letters. Which is the odd one out?
- A. Bookkeeper
- B. Committee (answer)
- C. Employee
- D. Beehive
Bookkeeper, employee and beehive each contain three e letters. Committee contains two.
12. Three numbers are perfect squares. Which is the odd one out?
- A. 10201
- B. 10404
- C. 10609
- D. 10818 (answer)
101 squared is 10201, 102 squared is 10404 and 103 squared is 10609. 104 squared is 10816, not 10818.