AppliedNumeric answer
How many sequences of four opening and four closing brackets are balanced, meaning no prefix ever has more closings than openings?
Answer with a number. Fractions, powers and expressions like 23/6 or C(52,5) are read correctly in practice.
The worked solution is in Premium
The answer, the full working and the one idea to take away – for this and all 1,322 questions in the bank. Answer it in practice and your working is marked, with a known mistake named when you make one.
Learn the method
Reported in interviews at
More counting and combinatorics questions
- Walking a grid, part 1 of 3Foundation
- Five distinct analysts are split into two teams.Applied
- Eight traders are paired up for a desk-swap day, four pairs in all, and the…Applied
- Five points are placed anywhere in a 1 × 1 square.Applied
- Walking a grid, part 2 of 3Applied
- A path from (0,0) to (5,5) takes unit steps right or up.Advanced