Unit Digit Problem: Identifying Numbers Ending in 7

Q: What exactly is a unit digit?

The unit digit is the digit in the ones place - the very last digit you see when reading from left to right. In $ 17 $, the unit digit is 7.

Q: Why isn't 71 the answer since it has a 7?

Great question! While $ 71 $ contains the digit 7, that 7 is in the tens place, not the units place. The unit digit of 71 is actually 1.

Q: How do I remember which digit is the unit digit?

Think of it as the "last digit" or the "rightmost digit". Just like when you read a sentence from left to right, the unit digit is the final digit you encounter.

Q: What about larger numbers like 1,247?

Same rule applies! In $ 1,247 $, the unit digit is still 7 - always look at the rightmost digit no matter how big the number gets.

Place Value Identification with Unit Digits

Which number has a unit digit of 7?

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Step-by-step written solution

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Understand the problem

Which number has a unit digit of 7?

Step-by-step solution

To solve this problem, let's examine the options provided and identify the number that ends in 7:

Option 1: $71$ - The units digit here is 1.
Option 2: $79$ - The units digit here is 9.
Option 3: $17$ - The units digit here is 7.
Option 4: $16$ - The units digit here is 6.

Looking at the units digit of each option, we can see that option 3 is the only number with a units digit of 7.

Therefore, the number that has a unit digit of 7 is $\boxed{17}$ .

Final Answer

$17$

Key Points to Remember

Essential concepts to master this topic

Unit Digit Rule: The unit digit is the rightmost digit in any number
Reading Technique: In 17, read right to left: 7 is units, 1 is tens
Verification: Check each option by identifying the rightmost digit only ✓

Common Mistakes

Avoid these frequent errors

Confusing the first digit with the unit digit
Don't look at the first digit when finding the unit digit = wrong answer every time! Students often think 71 has unit digit 7 because 7 comes first. Always look at the rightmost digit only.

Practice Quiz

Test your knowledge with interactive questions

What number do the blue squares below represent?

FAQ

Everything you need to know about this question

What exactly is a unit digit?

The unit digit is the digit in the ones place - the very last digit you see when reading from left to right. In $17$ , the unit digit is 7.

Why isn't 71 the answer since it has a 7?

Great question! While $71$ contains the digit 7, that 7 is in the tens place, not the units place. The unit digit of 71 is actually 1.

How do I remember which digit is the unit digit?

Think of it as the "last digit" or the "rightmost digit". Just like when you read a sentence from left to right, the unit digit is the final digit you encounter.

Does every number have a unit digit?

Yes! Every whole number has a unit digit. Even single-digit numbers like $7$ have themselves as the unit digit.

What about larger numbers like 1,247?

Same rule applies! In $1,247$ , the unit digit is still 7 - always look at the rightmost digit no matter how big the number gets.

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