Compare Numbers 17□ and 159: Finding the Missing Digit and Inequality Sign

Number Comparison with Missing Digits

There is an unknown digit behind the \Box

Determine the correct sign for the following expression:

17?159 17\Box?159

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1

Understand the problem

There is an unknown digit behind the \Box

Determine the correct sign for the following expression:

17?159 17\Box?159

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the range of possible values for 17 followed by a digit (Box).
  • Step 2: Compare each possible value against 159.

Now, let's work through each step:

Step 1: The number 17 followed by an unknown digit can be represented as 1717\Box, where \Box can be any digit from 0 to 9. This forms the numbers 170 to 179.

Step 2: We'll compare these numbers:

  • 170>159170 > 159
  • 171>159171 > 159
  • 172>159172 > 159
  • 173>159173 > 159
  • 174>159174 > 159
  • 175>159175 > 159
  • 176>159176 > 159
  • 177>159177 > 159
  • 178>159178 > 159
  • 179>159179 > 159

Since all possible values of 1717\Box (from 170 to 179) are greater than 159, the correct comparison sign is >>.

Therefore, the solution to the problem is >>.

3

Final Answer

>

Key Points to Remember

Essential concepts to master this topic
  • Range Analysis: Unknown digit creates numbers from 170 to 179
  • Technique: Compare smallest possibility: 170 > 159, so all are greater
  • Check: Test both extremes: 170 > 159 and 179 > 159 ✓

Common Mistakes

Avoid these frequent errors
  • Testing only one possible digit value
    Don't just check if 175 > 159 and assume that's the answer! The unknown digit could be any value from 0-9, giving different numbers. Always consider the complete range from 170 to 179 to ensure all possibilities lead to the same comparison result.

Practice Quiz

Test your knowledge with interactive questions

Which group contains numbers that are smaller in value than 87?

FAQ

Everything you need to know about this question

Do I need to check every single number from 170 to 179?

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Not necessarily! Since all numbers starting with 17 are at least 170, and 170 > 159, you can conclude that all possibilities are greater than 159.

What if the missing digit was in a different position?

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The position matters! If it were 17 1\Box7 , you'd get numbers from 107 to 197, giving different comparison results. Always identify which digit position is unknown.

Could the answer ever be 'equals' for this type of problem?

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Only if one of the possible numbers exactly matches the comparison number. For example, if comparing 15 15\Box to 159, then 159 would make them equal!

How do I know which comparison sign to use?

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Create the range of possible values first. If all values are greater than the comparison number, use >. If all are less, use <. If the range includes both greater and less values, there's no single correct answer.

What's the fastest way to solve this type of problem?

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  • Find the smallest possible value (170 in this case)
  • Find the largest possible value (179 in this case)
  • If both have the same relationship to 159, that's your answer!

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