Answer:
<em>19800 seconds, or 330 minutes, or 5 hours + 30 minutes</em>
Step-by-step explanation:
<u>Number Permutations</u>
We know the phone number has 7 digits, 4 of which are known by Mark. This leaves him 3 digits to guess with. We also know the last one is not zero. The number can be represented as
XXY
Where X can be any digit from 0 to 9 and Y can be any digit from 1 to 9. The first two can be combined in 10x10 ways, and the last one can be of 9 ways, this gives us 10x10x9 = 900 possible permutations.
If each possible number takes him 22 seconds, every possibility will need
22x900=19800 seconds, or 330 minutes, or 5 hours + 30 minutes
First off, let's take a look at what these numbers are:
Real numbers: It can be any numbers,both rational and irrational.
Natural numbers: The number has to be integer and positive.
Integers: A number without fraction or demical place.
Whole number: The number has to be natural and cannot be negative.
Therefore, as 12 is a positive number with no demical place or fraction, it is real numbers,integers, whole numbers, and natural numbers.
Hope it helps!
