The Potgieters have a party. The first time the doorbell rings, a guest enters. On the second ring, three guests enter. On the third ring, five guests enter, and so on. That is, on each successive ring the group entering is two more than the previous group. How many guests will enter on the 15th ring? How many guests will be present after the 15th ring?

Correct answer: 15th ring - enter 29 guests 15th ring - present 225

Step-by-step explanation:

After first ring 1 guest

After second ring 1+3 = 4 = 2² present

After third ring 4+5 = 9 = 3² present

After fourth ring 9+7 = 16 = 4²

After fifth ring 16+9 = 25 = 5²

and so on ...

After 15th ring 15² = 225 present

After 15th ring enter 225 - 196 = 29 guests

God is with you!