SAT Math Multiple Choice Practice Question 112: Answer and Explanation
2. A sequence of numbers is created by starting with k, and then adding 3 to the previous number to create each new number. If the 20th number in this sequence is 55, then k equals
Correct Answer: B
B. By the time you get to the 20th number, you've added three 19 times (not 20). Thus, you've added 19 × 3 = 57. Because you're now at 55, you must have started at 55 - 57 = -2.