Question

How many such $7s$ are there in the following number sequence each of which is immediately preceded by $1$ or $3$?
$17385713771739062973173$

• A. $3$
• B. $5$
• C. $6$
• D. $4$

Answer 1

Answer: (D)

$4$

$\underset{–}{1}738571\underset{–}{3}77\underset{–}{1}739062973\underset{–}{1}73$
There are four 7s are there immediately preceded by 1 or 3.