SOLUTION: A shop assistant was to stack 231 cereal boxes in a display window. The manager wanted all 231 boxes to be used and the boxes to be stacked in a triangle. x x x

Algebra ->  Average -> SOLUTION: A shop assistant was to stack 231 cereal boxes in a display window. The manager wanted all 231 boxes to be used and the boxes to be stacked in a triangle. x x x       Log On


   



Question 1143728: A shop assistant was to stack 231 cereal boxes in a display window. The manager wanted all
231 boxes to be used and the boxes to be stacked in a triangle.
x
x x
x x x
x x x x
How many boxes needed to be placed on the bottom row to build the
display and what is the equation to work it out?

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
want the sum of n numbers, which is n(n+1)/2
that equals 231
so n(n+1)=462
n^2+n-462=0
(n+22)(n-21)=0
positive root is n=21
boxes on the bottom row.