Solve 1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9

$$1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9$$

Evaluate

$$90$$

Solution Steps

Add 1 and 1 to get 2.

$$2+2+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9$$

Add 2 and 2 to get 4.

$$4+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9$$

Add 4 and 2 to get 6.

$$6+3+3+4+4+5+5+6+6+7+7+8+8+9+9$$

Add 6 and 3 to get 9.

$$9+3+4+4+5+5+6+6+7+7+8+8+9+9$$

Add 9 and 3 to get 12.

$$12+4+4+5+5+6+6+7+7+8+8+9+9$$

Add 12 and 4 to get 16.

$$16+4+5+5+6+6+7+7+8+8+9+9$$

Add 16 and 4 to get 20.

$$20+5+5+6+6+7+7+8+8+9+9$$

Add 20 and 5 to get 25.

$$25+5+6+6+7+7+8+8+9+9$$

Add 25 and 5 to get 30.

$$30+6+6+7+7+8+8+9+9$$

Add 30 and 6 to get 36.

$$36+6+7+7+8+8+9+9$$

Add 36 and 6 to get 42.

$$42+7+7+8+8+9+9$$

Add 42 and 7 to get 49.

$$49+7+8+8+9+9$$

Add 49 and 7 to get 56.

$$56+8+8+9+9$$

Add 56 and 8 to get 64.

$$64+8+9+9$$

Add 64 and 8 to get 72.

$$72+9+9$$

Add 72 and 9 to get 81.

$$81+9$$

Add 81 and 9 to get 90.

$$90$$

Factor

$$2\times 3^{2}\times 5$$