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#### A man is discovered dead sitting at his desk, alone in the locked office. He did not commit suicide and there was no weapons in the room. The only clue is a sealed envelope on the desk in front of him. How did he die?

**Answer: ** The envelope glue was poisoned and when the man licked the envelope to seal it, he died.

**Solution: **

#### How do you calculate 1+2+3+4+5+6+7+8+9+10 quickly?

**Answer: **55

**Solution: **

**Answer : 55**

The series “1+2+3+4+5+6+7+8+9+10” can be considered as the sum of the first 10 Natural numbers.

The generalized formula to find the sum of first N natural numbers is

(N * (N + 1) ) /2

For the series given, the value of N is 10

So substituting value of N in the generalized formula

( 10 * (10 + 1) ) / 2

= (10 * 11 ) / 2

= 110/2

Correct answer = 55

**Answer : 55**

The series “1+2+3+4+5+6+7+8+9+10” can be considered as the sum of the first 10 Natural numbers.

The generalized formula to find the sum of first N natural numbers is

(N * (N + 1) ) /2

For the series given, the value of N is 10

So substituting value of N in the generalized formula

( 10 * (10 + 1) ) / 2

= (10 * 11 ) / 2

= 110/2

Correct answer = 55

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