# Euler problems/71 to 80

(Difference between revisions)

## 1 Problem 71

Listing reduced proper fractions in ascending order of size.

Solution:

`problem_71 = undefined`

## 2 Problem 72

How many elements would be contained in the set of reduced proper fractions for d ≤ 1,000,000?

Solution:

`problem_72 = undefined`

## 3 Problem 73

How many fractions lie between 1/3 and 1/2 in a sorted set of reduced proper fractions?

Solution:

`problem_73 = undefined`

## 4 Problem 74

Determine the number of factorial chains that contain exactly sixty non-repeating terms.

Solution:

`problem_74 = undefined`

## 5 Problem 75

Find the number of different lengths of wire can that can form a right angle triangle in only one way.

Solution:

`problem_75 = undefined`

## 6 Problem 76

How many different ways can one hundred be written as a sum of at least two positive integers?

Solution:

`problem_76 = undefined`

## 7 Problem 77

What is the first value which can be written as the sum of primes in over five thousand different ways?

Solution:

`problem_77 = undefined`

## 8 Problem 78

Investigating the number of ways in which coins can be separated into piles.

Solution:

`problem_78 = undefined`

## 9 Problem 79

By analysing a user's login attempts, can you determine the secret numeric passcode?

Solution:

`problem_79 = undefined`

## 10 Problem 80

Calculating the digital sum of the decimal digits of irrational square roots.

Solution:

`problem_80 = undefined`