# Euler problems/11 to 20

## Contents

## Problem 11

What is the greatest product of four numbers on the same straight line in the 20 by 20 grid?

Solution:

```
problem_11 = undefined
```

## Problem 12

What is the first triangle number to have over five-hundred divisors?

Solution:

```
problem_12 = undefined
```

## Problem 13

Find the first ten digits of the sum of one-hundred 50-digit numbers.

Solution:

```
problem_13 = undefined
```

## Problem 14

Find the longest sequence using a starting number under one million.

Solution:

```
problem_14 = undefined
```

## Problem 15

Starting in the top left corner in a 20 by 20 grid, how many routes are there to the bottom right corner?

Solution:

```
problem_15 = undefined
```

## Problem 16

What is the sum of the digits of the number 21000?

Solution:

```
problem_16 = undefined
```

## Problem 17

How many letters would be needed to write all the numbers in words from 1 to 1000?

Solution:

```
problem_17 = undefined
```

## Problem 18

Find the maximum sum travelling from the top of the triangle to the base.

Solution:

```
problem_18 = undefined
```

## Problem 19

How many Sundays fell on the first of the month during the twentieth century?

Solution:

```
problem_19 = undefined
```

## Problem 20

Find the sum of digits in 100!

Solution:

```
problem_20 = undefined
```