Math Problem Statement

A pyramid of empty cans has 30 blocks in the bottom row and one fewer can in each successive row thereafter. How many cans are there in the pyramid

Solution

To find the total number of cans in the pyramid, we need to calculate the sum of the cans in all the rows.

The pyramid has 30 cans in the bottom row, and each successive row has one fewer can than the row below it. So the number of cans in the rows forms a sequence: 30, 29, 28, ..., 1.

This sequence is an arithmetic series where:

  • The first term a1=30a_1 = 30,
  • The last term an=1a_n = 1,
  • The common difference d=1d = -1.

The number of terms (rows) nn can be found using the formula: n=a1and+1=3011+1=30n = \frac{a_1 - a_n}{|d|} + 1 = \frac{30 - 1}{1} + 1 = 30

The sum SnS_n of the first nn terms of an arithmetic series is given by: Sn=n2×(a1+an)S_n = \frac{n}{2} \times (a_1 + a_n)

Substituting the values: S30=302×(30+1)=15×31=465S_{30} = \frac{30}{2} \times (30 + 1) = 15 \times 31 = 465

So, the total number of cans in the pyramid is 465.

Would you like further details or have any questions? Here are some related questions for further exploration:

  1. How would the formula change if the difference between each row's cans was 2 instead of 1?
  2. What is the total number of cans if the bottom row had 50 cans?
  3. Can you calculate the total number of cans if the bottom row had 30 cans but only every second row was counted?
  4. How many cans would there be if the bottom row had 30 cans and each successive row had two fewer cans?
  5. What would the total be if the pyramid had a geometric sequence instead?

Tip: When dealing with arithmetic series, always identify the first term, common difference, and the number of terms to use the sum formula effectively.

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Math Problem Analysis

Mathematical Concepts

Arithmetic Series
Summation of Series

Formulas

Arithmetic series sum formula

Theorems

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Suitable Grade Level

Grades 7-9