Find the Number After 20,000: Sequential Number Challenge

Q: What's the difference between predecessor and successor?

The predecessor is the number that comes before (subtract 1), while the successor is the number that comes after (add 1). For 20,000: predecessor = 19,999, successor = 20,001.

Q: What if the question asks 'What number am I?' instead of asking directly?

Read carefully! If it says 'The number before me is 20,000', then you are the number that comes after 20,000, which is 20,001. Always identify what the question is actually asking for.

Number Sequences with Predecessor Identification

The number before me is 20,000. What number am I?

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Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

The number before me is 20,000. What number am I?

Step-by-step solution

To determine the number that comes before 20,000, follow these steps:

Step 1: Start by identifying the given number, which is 20,000.
Step 2: Use the formula for finding the predecessor of a number $x$ , which is $x - 1$ .
Step 3: Perform the subtraction: $20,000 - 1$ .

Now, let's execute these steps:
Step 1: We know that the given number is 20,000.
Step 2: Applying the predecessor formula, we calculate $20,000 - 1$ .
Step 3: This results in $19,999$ .

Therefore, the number before 20,000 is $19,999$ .

Final Answer

$19,999$

Key Points to Remember

Essential concepts to master this topic

Rule: The predecessor of any number is that number minus 1
Technique: Calculate $20,000 - 1 = 19,999$ for the number before
Check: Verify that $19,999 + 1 = 20,000$ gives the original number ✓

Common Mistakes

Avoid these frequent errors

Confusing predecessor with successor
Don't add 1 to find the number before = 20,001 instead of 19,999! This gives you the successor (number after) not the predecessor (number before). Always subtract 1 to find the number that comes before.

Practice Quiz

Test your knowledge with interactive questions

Select the predecessor of the number 2100:

FAQ

Everything you need to know about this question

What's the difference between predecessor and successor?

The predecessor is the number that comes before (subtract 1), while the successor is the number that comes after (add 1). For 20,000: predecessor = 19,999, successor = 20,001.

Why can't I just change the last digit to 9?

That only works for numbers ending in digits 1-9! When a number ends in 0 (like 20,000), subtracting 1 affects multiple digits because you're borrowing across place values.

How do I handle borrowing with large numbers?

When subtracting 1 from 20,000, you borrow from the ten-thousands place all the way down: 20,000 becomes 19,999. Think of it as trading one ten-thousand for nine thousands, nine hundreds, nine tens, and nine ones.

Is there a pattern I can memorize?

Yes! When finding the predecessor of numbers ending in zero(s), replace the rightmost non-zero digit with one less, and change all zeros after it to 9s. So 20,000 → 19,999.

What if the question asks 'What number am I?' instead of asking directly?

Read carefully! If it says 'The number before me is 20,000', then you are the number that comes after 20,000, which is 20,001. Always identify what the question is actually asking for.

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