Question

Calculati: 3+6+9+...+300

Answer 1

3+6+9+...+300= 3(1+2+3+...+100) = $3* \frac{100*101}{2}=150*101 = 150*(100+1) = 15000+150 = 15150$

Answer 2

3+6+9+.........+300= 3×(1+2+3+...+100)= 3×100×101 / 2=15150