Solve 15×2×9: Three-Factor Multiplication Problem

Q: Does it matter which two numbers I multiply first?

No, it doesn't! You can multiply $ 15×2 $ first, or $ 2×9 $ first. The commutative property means you'll get the same answer either way: 270.

Q: Why do we work left to right with multiplication?

Working left to right is the standard convention that keeps everyone on the same page. It's like reading - we follow the same direction so there's no confusion about which operation to do first.

Q: Can I multiply all three numbers in my head?

For larger numbers like these, it's much easier to break it into steps. Calculate $ 15×2=30 $ first, then $ 30×9=270 $. This prevents errors!

Q: How can I check if 270 is the right answer?

Try a different order: $ 2×9=18 $, then $ 15×18=270 $. Or use estimation: $ 15×20=300 $, so 270 seems reasonable since $ 2×9=18 $ is less than 20.

Q: What if I accidentally calculated 15×2×9 as (15+2)×9?

That would give you $ 17×9=153 $ - one of the wrong answer choices! Always remember: × means multiply, + means add. Don't mix them up!

Order of Operations with Multiple Factors

Solve the following expression:

$15\times2\times9=$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Solve

00:02 Let's solve according to the order of operations, from left to right

00:06 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

Solve the following expression:

$15\times2\times9=$

Step-by-step solution

According to the order of operations rules, since the exercise has only multiplication, we will solve it from left to right:

$15\times2=30$

Now we will get the exercise:

$30\times9=$

We will calculate the exercise by putting aside the tens of the number 30 and solve the exercise:

$3\times9=27$

Now we can add the tens that we previously set aside, and add them to the result we got.

This way we will get the number:

$270$

Final Answer

$270$

Key Points to Remember

Essential concepts to master this topic

Rule: Multiply from left to right when only multiplication operations
Technique: First calculate $15×2=30$ , then $30×9=270$
Check: Verify by calculating differently: $2×9=18$ , then $15×18=270$ ✓

Common Mistakes

Avoid these frequent errors

Adding instead of multiplying all factors
Don't calculate $15+2+9=26$ when you see multiplication symbols! This gives completely wrong results because addition and multiplication are different operations. Always multiply when you see × symbols between numbers.

Practice Quiz

Test your knowledge with interactive questions

$$ 94+12+6= $$

FAQ

Everything you need to know about this question

Does it matter which two numbers I multiply first?

No, it doesn't! You can multiply $15×2$ first, or $2×9$ first. The commutative property means you'll get the same answer either way: 270.

Why do we work left to right with multiplication?

Working left to right is the standard convention that keeps everyone on the same page. It's like reading - we follow the same direction so there's no confusion about which operation to do first.

Can I multiply all three numbers in my head?

For larger numbers like these, it's much easier to break it into steps. Calculate $15×2=30$ first, then $30×9=270$ . This prevents errors!

How can I check if 270 is the right answer?

Try a different order: $2×9=18$ , then $15×18=270$ . Or use estimation: $15×20=300$ , so 270 seems reasonable since $2×9=18$ is less than 20.

What if I accidentally calculated 15×2×9 as (15+2)×9?

That would give you $17×9=153$ - one of the wrong answer choices! Always remember: × means multiply, + means add. Don't mix them up!

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