Calculate the Product: Solving (+9)×(-4) with Integer Multiplication

Q: Why is a positive times a negative always negative?

Think of it as repeated subtraction! $ (+9) \times (-4) $ means "take away 9 four times" or subtract 9 + 9 + 9 + 9 = 36 from zero, giving you -36.

Q: How do I remember the sign rules for multiplication?

Use this simple pattern: same signs give positive (+ × + = +, - × - = +) and different signs give negative (+ × - = -, - × + = -). Like friends agree, opposites disagree!

Q: What's the difference between (+9) and just 9?

There's no difference in value! Writing (+9) just makes the positive sign explicit. It's especially helpful when learning sign rules to see both signs clearly.

Q: Can I multiply the numbers first, then worry about the sign?

Absolutely! Many students find it easier to calculate $ 9 \times 4 = 36 $ first, then apply the sign rule: positive × negative = negative, so the answer is -36.

Q: What if I accidentally get +36 instead of -36?

Check your sign rules! You correctly multiplied the numbers but missed that different signs (+ and -) always give a negative result. Practice the sign patterns until they become automatic.

Integer Multiplication with Mixed Signs

$(+9)\times(-4)=$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Solve

00:03 Positive times negative is always negative

00:06 Calculate

00:09 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$(+9)\times(-4)=$

Step-by-step solution

Due to the fact that we are multiplying a positive number by a negative number, the result must be a negative number:

$+\times-=-$

Therefore:

$+9\times-4=-36$

Final Answer

$-36$

Key Points to Remember

Essential concepts to master this topic

Rule: Positive times negative always equals negative result
Technique: Calculate $9 \times 4 = 36$ , then apply negative sign
Check: Verify sign pattern: $(+) \times (-) = (-)$ gives -36 ✓

Common Mistakes

Avoid these frequent errors

Forgetting to apply the negative sign
Don't just multiply 9 × 4 = 36 and forget the signs! This ignores the sign rules and gives a positive result instead of negative. Always determine the sign first: positive × negative = negative, then calculate the numbers.

Practice Quiz

Test your knowledge with interactive questions

Solve the following exercise:

$(+6)\cdot(+9)=$

FAQ

Everything you need to know about this question

Why is a positive times a negative always negative?

Think of it as repeated subtraction! $(+9) \times (-4)$ means "take away 9 four times" or subtract 9 + 9 + 9 + 9 = 36 from zero, giving you -36.

How do I remember the sign rules for multiplication?

Use this simple pattern: same signs give positive (+ × + = +, - × - = +) and different signs give negative (+ × - = -, - × + = -). Like friends agree, opposites disagree!

What's the difference between (+9) and just 9?

There's no difference in value! Writing (+9) just makes the positive sign explicit. It's especially helpful when learning sign rules to see both signs clearly.

Can I multiply the numbers first, then worry about the sign?

Absolutely! Many students find it easier to calculate $9 \times 4 = 36$ first, then apply the sign rule: positive × negative = negative, so the answer is -36.

What if I accidentally get +36 instead of -36?

Check your sign rules! You correctly multiplied the numbers but missed that different signs (+ and -) always give a negative result. Practice the sign patterns until they become automatic.

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