Given:
First term of an arithmetic sequence is 2.
Sum of first 15 terms = 292.5
To find:
The common difference.
Solution:
We have,
First term: 
Sum of first 15 terms: 
The formula of sum of first n terms of an AP is
![S_n=\dfrac{n}{2}[2a+(n-1)d]](https://tex.z-dn.net/?f=S_n%3D%5Cdfrac%7Bn%7D%7B2%7D%5B2a%2B%28n-1%29d%5D)
Where, a is first term and d is common difference.
Putting , n=15 and a=2 in the above formula, we get
![292.5=\dfrac{15}{2}[2(2)+(15-1)d]](https://tex.z-dn.net/?f=292.5%3D%5Cdfrac%7B15%7D%7B2%7D%5B2%282%29%2B%2815-1%29d%5D)
![292.5=\dfrac{15}{2}[4+14d]](https://tex.z-dn.net/?f=292.5%3D%5Cdfrac%7B15%7D%7B2%7D%5B4%2B14d%5D)
![292.5=15[2+7d]](https://tex.z-dn.net/?f=292.5%3D15%5B2%2B7d%5D)
Divide both sides by 15.
Dividing both sides by 7, we get
Therefore, the common difference is 2.5.
Answer:
Step-by-step explanation:
The missing length is 13 because,
Lets say the top triangle is A and the bottom triangle is B.
Triangle A gives us the side GF, and Triangle B gives us the sides TU and ST. Since the triangles are similar(as stated in the problem), we can pair 2 sides GF(A) and TU(B) which is 11:22.(one way I usually figure which sides are similar is by first- matching the hypotenuse, then checking which of the remaining two is longer.. if that made any sense). You can see that their relationship is x2 or /2 (In another word, from A to B is multiplication- ex: 11 * 2 is 22, and from B to A is division- ex 22/2 is 11.) Since the missing number is the hypotenuse of triangle A and you know the Hypotenuse of triangle B all you have to do is divide side TS by 2 to get side SF. So the missing side is 13.
Answer: 13
86921 = 80000 + 6000 + 900 +20 +1
B. V=9
Multiply it out, then subtract 99 from both sides, then divide by 11
