/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 17 Grains of wheat on a chess board... [FREE SOLUTION] | 91Ó°ÊÓ

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Grains of wheat on a chess board: A children's fairy tale tells of a clever elf who extracted from a king the promise to give him one grain of wheat on a chess board square today, two grains on an adjacent square tomorrow, four grains on an adjacent square the next day, and so on, doubling the number of grains each day until all 64 squares of the chess board were used. How many grains of wheat did the hapless king contract to place on the 64th square? There are about \(1.1\) million grains of wheat in a bushel. Assume that a bushel of wheat sells for \(\$ 4.25\). What was the value of the wheat on the 64th square?

Short Answer

Expert verified
The king promised 9.2 quintillion grains; the wheat's value on the 64th square is approximately \(\$35,460,352,000,000\).

Step by step solution

01

Understanding Exponential Growth

The problem states that the number of grains doubles each day starting from the first square with one grain. This can be represented by the formula for the number of grains on the nth square: \( 2^{n-1} \). For the 64th square, substitute \( n = 64 \) into the formula.
02

Calculate the Grains on the 64th Square

Substitute \( n = 64 \) into the formula \( 2^{n-1} \) to get \( 2^{64-1} = 2^{63} \). Calculate \( 2^{63} \) to find the number of grains on the 64th square.
03

Convert Grains to Bushels

Since there are about \( 1.1 \) million grains in a bushel, divide the total grains on the 64th square by \( 1,100,000 \) to convert grains to bushels: \( \frac{2^{63}}{1,100,000} \).
04

Calculate the Value in Dollars

Multiply the number of bushels by the cost per bushel (\( \$4.25 \)) to find the total value of the wheat. This gives \( \text{Bushels} \times 4.25 \) dollars.
05

Summary and Final Result

Summarize the total number of grains on the 64th square and convert it into bushels and then into dollars. Provide the financial implication based on the market price.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Geometric Series
A geometric series is a sum of numbers where each term is a constant multiple of the previous one. It's a powerful concept used to express sequences where the pattern involves multiplication by a fixed number. In the fairy tale with the chessboard and grains of wheat, doubling each day represents a geometric series. Each day or square doubles the previous count. Let's break it down:
  • The first term is 1 grain on the first square.
  • The second term is 2 grains on the second square.
  • The series continues like this: 1, 2, 4, 8, and so on.
This is a classic example of a geometric series with a common ratio of 2. The formula for finding the sum of a geometric series can be quite handy in such problems. However, when it comes to doubling sequences, understanding how quickly the numbers grow is often more critical than adding them up. You will see that each term grows exponentially, highlighting the concept of exponential growth through geometric progression.
Powers of Two
The powers of two play a vital role in many mathematical contexts, including the fascinating chessboard problem. When you hear 'powers of two,' think of the sequence created by continually doubling: 2, 4, 8, 16, and so forth. It is expressed mathematically as:\[2^n\]Where \( n \) represents the number of times you multiply 2 by itself. In our chessboard scenario, when figuring out the number of grains on any given square, the formula used is \( 2^{n-1} \), representing the grains on the nth square. For instance, the second square has \( 2^{2-1} = 2^1 = 2 \) grains.

In specifically calculating for the 64th square, you use:\[2^{64-1} = 2^{63}\]Each square number gets exponentially larger, emphasizing how quickly exponential growth can increase to massive numbers. Powers of two are not only integral to mathematical problems like these but also appear prominently in computer science and binary systems.
Chessboard Problem
The chessboard problem is a classic illustration of exponential growth, often used to teach the powerful implications of geometric sequences. Here's a summary:
  • The problem starts with one grain on the first square.
  • Every subsequent square doubles the grains from the previous, thanks to exponential growth.
  • By the time we reach the 64th square with our doubling method, the number of grains becomes incredibly large.
Using \( 2^{63} \), we describe how the number of grains balloons to a sum that's practically astronomical. The tale is a parable showing the naive underestimation of exponential numbers when the king agrees to the supposedly innocent terms. Once you visualize each square as a successive doubling, it becomes clear how quickly values can spiral out of control. This problem remains a favorite example among educators to illustrate the impact of geometric progression.
Mathematical Problem Solving
Mathematical problem solving often requires breaking down complex problems into manageable steps, just as we did in the chessboard example. Here are some effective strategies:
  • Understand the Problem: Read the problem carefully to understand the sequence or pattern, like identifying that grains double daily on the chessboard.
  • Select a Strategy: Choose an appropriate mathematical formula or concept. In this case, the formula \( 2^{n-1} \) for determining the number of grains per square is crucial.
  • Work Out the Steps: Calculate using the formula to find values step by step—locating \( 2^{63} \) for the 64th square.
  • Convert and Interpret: Sometimes your raw result needs conversion, like translating grains to bushels or dollars for practical insights.
Remember, problem solving in math is about clarity, breaking tasks into achievable chunks, and verifying assumptions, helping ensure the solution meets all initial conditions.

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Most popular questions from this chapter

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