Calculate the Deficit: $10 Budget vs $20 Purchase Problem

Subtraction with Negative Results

Daniel has 10.Hewantstobuyapackofcookiesfor10. He wants to buy a pack of cookies for 20.

How much money will Daniel have left if he buys the cookies?

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Daniel has 10.Hewantstobuyapackofcookiesfor10. He wants to buy a pack of cookies for 20.

How much money will Daniel have left if he buys the cookies?

2

Step-by-step solution

To solve this problem, let's work through it step-by-step:

  • Step 1: Identify what Daniel has and what he wants to do.
  • Step 2: Use the subtraction operation to calculate the money left after the purchase.

Step 1: Daniel starts with \10 \).
Step 2: He wants to buy cookies costing \20 \).

Using the subtraction formula to find the remaining money:

\text{Remaining Money} = \10 - \2020

This calculation yields:

\10 - \20 = -\10\)

This result means Daniel will have -\10\) left, indicating he lacks 10 to make this purchase.

The correct solution to the problem is \(\boxed{-10}.

3

Final Answer

10 -10

Key Points to Remember

Essential concepts to master this topic
  • Rule: When purchase cost exceeds available money, result is negative
  • Technique: Calculate 1010 - 20 = -$10 to find deficit
  • Check: Negative answer means Daniel needs $10 more to buy cookies ✓

Common Mistakes

Avoid these frequent errors
  • Thinking you can't have negative money left
    Don't avoid negative answers or flip the subtraction to get positive = wrong understanding! This ignores the real situation where someone lacks sufficient funds. Always accept negative results as they show how much additional money is needed.

Practice Quiz

Test your knowledge with interactive questions

a is negative number.

b is negative number.

What is the sum of a+b?

FAQ

Everything you need to know about this question

What does it mean when I get a negative answer for money left?

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A negative result means the person doesn't have enough money! The negative number shows how much more money they need. In this case, Daniel needs $10 more to buy the cookies.

Should I write the answer as -$10 or just say he can't buy it?

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Always write -$10 as your mathematical answer! This shows exactly how much Daniel is short, which is more useful than just saying 'he can't afford it.'

Can someone really have negative money?

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In real life, this represents a deficit or debt. If Daniel borrowed money to buy the cookies, he'd owe $10. The math shows the shortage clearly.

Why don't we subtract 10from10 from 20 instead?

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The problem asks how much Daniel has after the purchase, so we subtract the cost from his current amount: \10 - \2020 . Flipping it would answer a different question!

How do I know when to expect a negative answer?

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Look for clues: when the amount being subtracted is larger than what you start with, expect a negative result. This happens in deficit or shortage problems.

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