Question

A grocer stacks oranges in a four-sided pyramid that is 7 layers high. How many oranges are in the pile?

Answer 1

Short Answer D
P(1) = 1(1+1)(2*1 + 1)/6
P(1) = 1(2)(2 +1) / 6
P(1) = 1(2)(3)/6
P(1) = 1

P(2) = 2(2+1)(2*2 + 1) / 6
P(2) = 2(3)(5) / 6
P(2) = 5 So this formula is adding as it goes along. To Find the Total all we need do is use the formula to calculate P(1) to P(7)

P(7) = 7*(7 + 1)(2*7 + 1)/6
P(7) = 7 * 8 * 15 / 6
P(7) = 7 * 4 * 5 
P(7) = 140 <<<< Answer