Answer:
A!
Step-by-step explanation:
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
1)
n 1 2 3 4 5 6
f(n) 1033 932 831 730 629 528
First term (a₁): <u>1033 </u> Common difference (d): <u>-101 </u>
Explicit rule: Recursive rule:
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2)
n 1 2 3 4 5 6
f(n) -39 -29 -19 -9 9 19
First term (a₁): <u> -39 </u> Common difference (d): <u> +10 </u>
Explicit rule: Recursive rule:
***********************************************************************************
3)
n 1 2 3 4 5 6
f(n) 3.75 2.5 1.25 0 -1.25 -2.5
First term (a₁): <u> 3.75 </u> Common difference (d): <u> -1.25 </u>
Explicit rule: Recursive rule: