An arrangement of marbles has 12 marbles in the first row and 10 rows in all. In each successive row one marble is added.What is
2 answers:
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Answer:
66
Step-by-step explanation:
If there are <em>n</em> students, then the number of pairs is .
With 12 students, pairs can be formed.
The reason the formula works is this: Each of the 12 students can be paired with 11 other students (no student is paired with him/her self). But counting 12 x 11 = 132 counts each pair <u>twice</u>. Example: student A can be paired with student B,..., student B can be paired with student A. The pair was counted two times.
See the attached image that shows pairings of 5 students. There are
5(5 - 1)/2 = 5(4)/2 = 10 pairs.
Answer:
(2,-5) and (2,1).
Step-by-step explanation:
We need to find the find all the points having an x coordinate of 2 whose distance from the point (-2,-4) is 5.
A circle with center (-2,-4) and radius 5 represents all the points whose distance from the point (-2,-4) is 5.
Standard form of a circle is
where, (h,k) is center and r is the radius.
Now, put x=2.
Taking square root on both sides.
So, the y-coordinates of the points are -5 and 1.
Therefore, the required points are (2,-5) and (2,1).