Great Grampa is more than 7 times David’s age, so he must be older than 77 (7 × 11). Since Great Aunt Sarah was born in February of 1920, she is 88 now. So Great Grampa must be an age from 78 through 87. Since Great Grampa says his age is not an even number, you can cross off 78, 80, 82, 84, and 86 from your list. You can also cross off 79, 83, and 85 because they are not divisible by 3. That leaves 81 and 87 as possibilities. Now, if second cousin Jake is 2 × 11 + 6, he must be 28. And if Great Grampa is more than 3 times Jake’s age, he must be older than 84 (3 × 28). Therefore, Great Grampa will be 87 on his upcoming birthday.

“But how are we going to fit all those candles on the cake?” David asks his father.

“All what candles, Davie? There’s only going to be one on the top. You know Great Gramps doesn’t like to tell his age.”