CHALLENGE FOR YOU COLLEGE PEOPLE What is (5a -7b + 3) + (2a - 6b + 5c - 12)?
1 answer:
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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:
There are 650 cannonballs
Step-by-step explanation:
If you look closely in the picture, you can see that:
- 1st row has 1 ball
- 2nd row has 4 balls
- 3rd row has 9 balls
- 4th row has 16 balls
etc. etc.
We can see that the number of balls is the square of the row number. There are a total of 12 rows. So, rest of the rows has:
- 5th row has 25 balls
- 6th row has 36 balls
- 7th row has 49 balls
- 8th row has 64 balls
- 9th row has 81 balls
- 10th row has 100 balls
- 11th row has 121 balls
- 12th row has 144 balls
If we add up all those, we get total number of balls:
There are 650 cannonballs