View All num of num See all Photos Jane Street This employer has taken extra steps to respond to reviews and provide job seekers with accurate company information, photos, and reviews. Interested for your company?Learn More. www.janestreet.com Profile Unclaimed Overview Reviews Salaries Interviews Jobs Photos Benefits 19 Reviews 57 Salaries 539 Interviews Follow Add Review or Salary Follow Add Review or Salary Interview Question Trader Intern Interview New York, NY Jane Street What is the smallest number divisible by 225 that consists of all 1s and 0s? Tags: See more , See less 8 Answer Add Tags Answer Interview Answer 6 Answers ▲ 7 ▼ 11111111100 Interview Candidate on 12-Oct-2010 ▲ 16 ▼ Two facts to note are:1) Multiplies of 225 end in 00 25 50 752) A number is divisible by 9 if the digits sum to 9.Only those multiples ending in 00 could have only 1's and 0's.So, the smallest digit we can multiply 225 by to get 00 at the end is 4. That is,225*4=900. Now, we want to find the smallest multiple of 900 that contains only 1's and 0's. Let us first focus on 9 and then tack on the 00 after. The smallest multple of 9 with only 1's and 0's is 111111111. This is a consquence of the fact that the digits must sum to 9. Now, we tack on the 00 at the end and obtain 11111111100. Interview on 19-Jan-2011 ▲ 0 ▼ WRONG1111111110.Think of 225 as (5)^2(9). So this number must end in a 0 to be divisible by 5. Since every number that 5 divides ends in a 5 or 0, that number is also divisible by 5. Since a number divisible by 9 must have the digits sum to a number divisible by 9, then all we need is 9 1's and a 0 on the end for 1111111110. Anonymous on 06-Jul-2012 ▲ 4 ▼ 1111111110 / 225 = 4938271.6 Anonymous is wrong on 14-Jul-2012 ▲ 0 ▼ I fail to understand the above answers. Shouldn't it be 225 or 2250. 225/225 =1 and 2250/225 =10. Both these numbers contain just 1's and 0's:P Anonymous on 11-Oct-2013 ▲ 1 ▼ The above answers seem too complicated/not explained at all.First, notice that 225 = 25 * 9.(1) A number is divisible by 9 iff the sum of its digits is divisible by 9 => we must have 9 1's in our number.(2) A number is divisible by 25 iff the last two digits are divisible by 25 => our last two digits must be 0's.Putting (1) and (2) together, our number is 11111111100. Anonymous on 09-Sep-2014 Add Answers or Comments To comment on this, Sign In or Sign Up.