Friday

March 6, 2015

March 6, 2015

Posted by **Melissa** on Wednesday, October 7, 2009 at 7:20pm.

I need help.. how do I work this? Step by step please.

- 7th grade math -
**jim**, Wednesday, October 7, 2009 at 8:23pmThe counting principle is oddly-named, since it mostly involves multiplying :-)

It just means that if you can do the first thing x ways, and then in the next step you can do that y ways, then overall you can do the whole thing in x * y ways.

Consider a two-digit PIN.

How many ways can you choose the first digit? 0 through 9 is ten digits, so that's 10 ways.

Choosing the second digit is the same. You can still choose any digit, including the one you picked for the first digit. This makes your second choice _independent_ of your first choice. Your first choice doesn't influence your second. So that's 10 ways.

So the counting principle says that you can choose a 2-digit PIN in 10 * 10 ways.

Move on to the third digit. Um, 10 ways again! This is getting familiar.

And the fourth?

So your answer is?

And as a sanity check, consider that the PIN you must have chosen is an integer between or including 0000 through 9999. How many numbers is that?

**Answer this Question**

**Related Questions**

Calculus - A farmer wishes to enclose a long rectangular pin that will then be ...

math - How many 5-digit bank security Personal Identification Numbers (PIN) ...

7th grade - USING THE FUNDAMENTAL COUNTING PRICIPLE TO FIND THE TOTAL NUMBER OF ...

Grade 9 Algebra Question 3 - TRIANGULAR NUMBERS By arranging bowling pins in ...

Math - Each digit of a four-digit PIN can be any number from 0 to 9. What is the...

MATH PLEASE HELP!!!!! - Ms. Goldfarb has 12 turquoise beads and 3 times as many ...

math - ms.goldfarb has 12 turqoise beads and 3 times as many amber beads. she is...

Math PLEASE - It's about arithmetic sequence . . (the sum) SOLUTION PLEASE THANK...

Math PLEASE - It's about arithmetic sequence . . (the sum) SOLUTION PLEASE THANK...

algebra (inequalities) - your club is in charge of making pins that students can...