YOUR TURN
1 + 2 + 3 + … + 100 = ?
Add them all.
Show the answer
5050
On the calculator: 
1 
100 
With pen and paper: 50 × (1 + 100) → 50 × 101 → 5050
1 + 2 + 3 + … + 100 = ?
Add them all.
5050
On the calculator: 1 100
With pen and paper: 50 × (1 + 100) → 50 × 101 → 5050