Wednesday

July 23, 2014

July 23, 2014

Posted by **Vivian** on Wednesday, March 14, 2012 at 8:14am.

A. I the bottom row of the display has 144 books and there is one book on the top, determine how many rows of books are in her pyramid.

B. Explain how to find the total number of books in the display.

C. If she removes the top four rows, how many books are left in the pyramid display?

- math -
**Reiny**, Wednesday, March 14, 2012 at 8:34amYou might want to make a sketch to show that the bottom level is a 12 by 12 square

the second level is a 11 by 11 square, etc

So your sum is 12^2 + 11^2 + 10^2 + ... 2^2 + 1^2

you could just add up these numbers to get 650

or you could use a formula that says

the sum of squares of consecutive numbers from 1 to n is

n(n+1)(2n+1)/6 which gives us 650

for the last part, find the sum of books removed at the top and subtract that from 650

btw, did you realize that the books would have to be square in shape?

**Related Questions**

help - a store does a display of 200 balls, he places them in the shape of a ...

math - A book is 1 3/4 inches thick. There are 8 copies of the same book stacked...

math - A book is 1 3/4 inches thick. There are 8 copies of the same book stacked...

English Grammar - 1. book shop / bookshop 2. book store / bookstore Are both ...

algebra2 - you are creating a window display at a toy store using wooden blocks...

math - You are the buyer for your university bookstore. One of the textbooks has...

math variation ques - The price, $C, of printing n copies of a book is partly ...

Geometry - 1 How many faces does a square pyramid have? 2 How many edges does a ...

Physics - A student presses a book between his hands. The forces that he exerts ...

physics, - A student presses a book between his hands The forces that he exerts ...