Question

You a Miguel Cervantes de Navas y Colon, captain in the Royal Spanish Army in Seville in the year 1842. Outside your barracks window is a stack of cannonballs, as shown in the illustration. On an idle afternoon you decide to calculate the number of cannonballs in the stack. what is the number of cannonballs.

Answer 1

Answer: 650

Explanation:

You gotta count them down

Answer 2

650 cannonballs

Explanation step by step:

• upper layer = 1 ^ 2

• second layer = 2 ^ 2

• third layer = 3 ^ 2

layer 12 is 12 ^ 2

The formula is:

n * (n + 1) * (2n + 1) / 6

n = 12

12 (12 + 1) (2 * 12 + 1) / 6

12 * 13 * 25/6 =

650

There are 650 cannonballs in this pyramid.