Step-by-Step Solution
They are 105, 120, 135, 150, 165, 180 and 195 — seven of them.(15×7=105 is the first one past 100 and 15×13=195 is the last one below 200.) The trap is 13, which counts every multiple of 15 from the beginning instead of only those inside the range.
Answer: A) 7
Key idea: Multiples are unlimited
The multiples of 7 are 7, 14, 21, 28, 35, … — you get them by multiplying 7 by 1, 2, 3, 4, 5, …. Multiples never run out. Every number is a multiple of itself (and of 1). 0 is a multiple of every number, but we usually exclude it when listing multiples for practical work.