diff --git a/project_euler/README.md b/project_euler/README.md index 9f77f719f..89b6d63b5 100644 --- a/project_euler/README.md +++ b/project_euler/README.md @@ -37,21 +37,77 @@ PROBLEMS: 7. By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the Nth prime number? + +8. Find the consecutive k digits in a number N that have the largest product. 9. A Pythagorean triplet is a set of three natural numbers, a < b < c, for which, a^2 + b^2 = c^2 There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product abc. +10. Find sum of all prime numbers below 2 million. + +11. In the given 20x20 grid, find 4 adjacent numbers (horizontally, vertically or diagonally) that have the largest product. + +12. The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be: + + 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ... + + Let us list the factors of the first seven triangle numbers: + + 1: 1 + 3: 1,3 + 6: 1,2,3,6 + 10: 1,2,5,10 + 15: 1,3,5,15 + 21: 1,3,7,21 + 28: 1,2,4,7,14,28 + We can see that 28 is the first triangle number to have over five divisors. + + What is the value of the first triangle number to have over five hundred divisors? + +13. Work out the first 10 digits of the sum of the given hundred 50 digit numbers. + 14. The following iterative sequence is defined for the set of positive integers: n → n/2 (n is even) n → 3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence: 13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1 Which starting number, under one million, produces the longest chain? + +15. Starting from top left corner of a 20x20 grid how many routes are there to reach the bottom left corner? 16. 2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26. What is the sum of the digits of the number 2^1000? + +17. If the numbers 1 through 1000 were written in words, how many total letters would be used? + +18. By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23. + 3 + 7 4 + 2 4 6 +8 5 9 3 + +That is, 3 + 7 + 4 + 9 = 23. + +Find the maximum total from top to bottom of the triangle below: + + 75 + 95 64 + 17 47 82 + 18 35 87 10 + 20 04 82 47 65 + 19 01 23 75 03 34 + 88 02 77 73 07 63 67 + 99 65 04 28 06 16 70 92 + 41 41 26 56 83 40 80 70 33 + 41 48 72 33 47 32 37 16 94 29 + 53 71 44 65 25 43 91 52 97 51 14 + 70 11 33 28 77 73 17 78 39 68 17 57 + 91 71 52 38 17 14 91 43 58 50 27 29 48 + 63 66 04 68 89 53 67 30 73 16 69 87 40 31 +04 62 98 27 23 09 70 98 73 93 38 53 60 04 23 + 20. n! means n × (n − 1) × ... × 3 × 2 × 1 For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800, and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.