Answer:
is proved for the sum of pth, qth and rth terms of an arithmetic progression are a, b,and c respectively.
Step-by-step explanation:
Given that the sum of pth, qth and rth terms of an arithmetic progression are a, b and c respectively.
First term of given arithmetic progression is A
and common difference is D
ie.,
and common difference=D
The nth term can be written as

pth term of given arithmetic progression is a

qth term of given arithmetic progression is b
and
rth term of given arithmetic progression is c

We have to prove that

Now to prove LHS=RHS
Now take LHS




![=\frac{[Aq+pqD-Dq-Ar-prD+rD]\times qr+[Ar+rqD-Dr-Ap-pqD+pD]\times pr+[Ap+prD-Dp-Aq-qrD+qD]\times pq}{pqr}](https://tex.z-dn.net/?f=%3D%5Cfrac%7B%5BAq%2BpqD-Dq-Ar-prD%2BrD%5D%5Ctimes%20qr%2B%5BAr%2BrqD-Dr-Ap-pqD%2BpD%5D%5Ctimes%20pr%2B%5BAp%2BprD-Dp-Aq-qrD%2BqD%5D%5Ctimes%20pq%7D%7Bpqr%7D)




ie., 
Therefore
ie.,
Hence proved
The area of the cross-section is 169 sq. cm.
That is the correct answer to this problem
On google, it says 8.463.
Answer:
6
Step-by-step explanation:
fred has 2 peanut butter and 3 jelly
type 1 peanut butter can go with all three types of jelly = 3 pb&js where ther is one constant peanutbutter and 3 different jellys
type 2 peanut butter can go with all three jellies = 3 pb&js where there is one constant peanutbutter and 3 different jellies
3+3=6
there are 6 peanut butter and jelly sandwhiches he could make.
you can also just multiply the numbers (2x3=6)