Shubham has to make a telephone call to his friend Nisheeth, Unfortunately he does not remember the 7 digit phone number. But he remembers that the first three digits are 635 or 674, the number is odd and there is exactly one 9 in the number. The maximum number of trials that Shubham has to make to be successful is N then (N–3400) is equal to
Text Solution
Verified by Experts2
(2)
Sol. Let the number starts with 635 then two cases arise
Case-1 If 9 occurs at units place then the number of numbers = 9 × 9 × 9 = 729
Case-2 If 9 does not come at units place then number of ways for 9 to occur at either of the rest three places = 3 C 1 = 3
the number of numbers = 3 × 9 × 9 × 4 = 972
total numbers starting with 635 = 729 + 972 = 1701
Similarly total number starting with 674 = 1701
Maximum number of trials = 1701 × 2 = 3402
──────────────────────────────────────────────────────────────────────────────────────────
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems