# Adding a Sequence of Numbers

Below we will cover a math trick to add a sequence in the form: 1 + 2 + ... + n:

Look at sequence 1 + 2 + ... + 14 = ?.

- Multiply the last number in the sequence (14) by 1 number higher (15). Then divide by 2.
- (14 * 15) / 2 = 105.
- To make the math easier you can simplify to 7 * 15 = 105.

**ANSWER is 105.**

Look at sequence 2 + 3 + ... + 31 = ?.

- Multiply the last number in the sequence (31) by 1 number higher (32). Then divide by 2.
- (31 * 32) / 2 = ?.
- Simplify to 31 * 16 = 496
- Use the FOIL Method if you need a trick to multiply two digit numbers.

- Subtract 1 from 496 since the sequence started with 2.

**ANSWER is 495.**

Watch the math video below for a detailed explanation!

### Practice Math Problems

- 1 + 2 + ... + 24 = ?
- 1 + 2 + ... + 8 = ?
- 1 + 2 + ... + 41 = ?
- 2 + 3 + ... + 37 = ?