<span>There are several ways to do this problem. One of them is to realize that there's only 14 possible calendars for any year (a year may start on any of 7 days, and a year may be either a leap year, or a non-leap year. So 7*2 = 14 possible calendars for any year). And since there's only 14 different possibilities, it's quite easy to perform an exhaustive search to prove that any year has between 1 and 3 Friday the 13ths.
Let's first deal with non-leap years. Initially, I'll determine what day of the week the 13th falls for each month for a year that starts on Sunday.
Jan - Friday
Feb - Monday
Mar - Monday
Apr - Thursday
May - Saturday
Jun - Tuesday
Jul - Thursday
Aug - Sunday
Sep - Wednesday
Oct - Friday
Nov - Monday
Dec - Wednesday
Now let's count how many times for each weekday, the 13th falls there.
Sunday - 1
Monday - 3
Tuesday - 1
Wednesday - 2
Thursday - 2
Friday - 2
Saturday - 1
The key thing to notice is that there is that the number of times the 13th falls upon a weekday is always in the range of 1 to 3 days. And if the non-leap year were to start on any other day of the week, the numbers would simply rotate to the next days. The above list is generated for a year where January 1st falls on a Sunday. If instead it were to fall on a Monday, then the value above for Sunday would be the value for Monday. The value above for Monday would be the value for Tuesday, etc.
So we've handled all possible non-leap years. Let's do that again for a leap year starting on a Sunday. We get:
Jan - Friday
Feb - Monday
Mar - Tuesday
Apr - Friday
May - Sunday
Jun - Wednesday
Jul - Friday
Aug - Monday
Sep - Thursday
Oct - Saturday
Nov - Tuesday
Dec - Thursday
And the weekday totals are:
Sunday - 1
Monday - 2
Tuesday - 2
Wednesday - 1
Thursday - 2
Friday - 3
Saturday - 1
And once again, for every weekday, the total is between 1 and 3. And the same argument applies for every leap year.
And since we've covered both leap and non-leap years. Then we've demonstrated that for every possible year, Friday the 13th will happen at least once, and no more than 3 times.</span>
Answer:
-2
Step-by-step explanation:
x^2 + x=2
Subtract 2 from each side
x^2 + x-2=2-2
x^2 + x-2=0
Factor
What 2 numbers multiply to -2 and add to 1
2*-1 = -2
2+-1 =1
(x-1)(x+2)=0
Using the zero product property
x-1 = 0 x+2 = 0
x=1 x = -2
Product of the roots
1*-2 = -2
Hi there!
So here's the important information we know:
He makes 15% comission on everything he sells
He sells a laptop for $293
To find out how much money Daniel makes in comission for the laptop, you need to calculate 15% of $293, which is the same thing as multiplying 15% by $293 :
15% × 293 = $
0.15 × 293 = $
43,95 = $
So your answer is: If Daniel sells a laptop for $293, he makes a comission of $43,95.
There you go! I really hope this helped, if there's anything just let me know! :)
The dog with the weight of 110lbs is the outlier in the equation--since the other dogs only range from 20 to 35 lbs.
