A child is creating a pyramid with building blocks. The top three levels include 4 blocks, 10 blocks, and 16 blocks.

Part 1: How many blocks would be needed for a pyramid 25 levels tall?

Part 2: Use complete sentences to explain how a sum of an arithmetic series was applied.

Question

A child is creating a pyramid with building blocks. The top three levels include 4 blocks, 10 blocks, and 16 blocks. 

Part 1: How many blocks would be needed for a pyramid 25 levels tall? 

Part 2: Use complete sentences to explain how a sum of an arithmetic series was applied.

anonymous · Answer

This is an aritmetic sequence so nth term is a+(n-1)d

So Part one, the answer is 148 blocks

campbell_st · Answer

the above solution is incorrect... 

you need to find the sum of the arithmetic series.... 


the solution above @mayayamfundo is the number of blocks needed for the last row... 

so using a = 4 l = 148 and n = 25

use the sum of an arithmetic sequence 

$$S_{n} = \frac{n}{2}[ a + l]$$   

just substitute and evaluate

anonymous · Answer

so it's not 148?

campbell_st · Answer

nope... that is how many blocks are in the 25th row... you are being asked to find how many blocks are needed to build a pyramid 25 row high...

anonymous · Answer

Um no... part 1 says How many blocks would be needed for a pyramid 25 levels tall?

anonymous · Answer

snap.... yeah you're right @campbell_st

anonymous · Answer

You guys i'm still confused

anonymous · Answer

@campbell_st please help