Question

Social security numbers have the form XXX-XX-XXXX,

where each X is a digit. How many unique social security
numbers are possible?
A) 100 million
B) almost 400 million
C) 1 billion
D) over 3 billion

Pamela chose B as the correct answer. How did she get that answer?

Please answer both parts.

Answer 1

C

Explanation

So you take the amount of digits total (which is 9) and the highest number you can make is 999,999,999 so basically everything between 000,000,0001 and 999,999,999 is a possible unique social security number. So its closest to 1 billion.

Pamela got B since the only logical explanation i can think of is that she rounded incorrectly

Answer 2

there is only a certain amount of numbers

i hope this helped you