Q) A website currently has a bank of 770 questions with two new questions added every three days. A student has already completed 300 of the questions and plans on completing one question per day moving forward. In how many days will the student have completed all the questions available to her ?

My Answer - 1406

My Approach - Since a student completes one question in 1 day, So in 3 days she solves 3 questions. But after every 3 days 2 more questions are added to the bank.

So in a span of 3 days, she reduces the number of questions to be solved by 1.

So initially she has 470 questions to solve, so after 1404 (468*3) days she will have left with 2 questions to solve. And by day 1406 she would have solved all the questions.

So the answer should be 1406 (rather than 1410 mentioned in the Video Solution)

@gregmat