The answer to your question is 136, pretty self explanatory
The sum of any arithmetic sequence is the average of the first and last terms times the number of terms.
Any term in an arithmetic sequence is:
a(n)=a+d(n-1), where a=initial term, d=common difference, n=term number
So the first term is a, and the last term is a+d(n-1) so the sum can be expressed as:
s(n)(a+a+d(n-1))(n/2)
s(n)=(2a+dn-d)(n/2)
s(n)=(2an+dn^2-dn)/2
However we need to know how many terms are in the sequence.
a(n)=a+d(n-1), and we know a=3 and d=2 and a(n)=21 so
21=3+2(n-1)
18=2(n-1)
9=n-1
10=n so there are 10 terms in the sequence.
s(n)=(2an+dn^2-dn)/2, becomes, a=3, d=2, n=10
s(10)=(2*3*10+2*10^2-2*10)/2
s(10)=(60+200-20)/2
s(10)=240/2
s(10)=120
Answer:
3. D 4. B hope this helped :)
$5,182.12
or
$3,367.88
I think it's one these two.
D. 360 cm squared
Explanation:
Multiply each faces edges.
18x7(WxL)
3x6(HxW)
3x18(HxL)
multiply each equations answer by 2, because the opposite face is the same.
108x2=216
18x2=36
54x2=108
add these together to get 360 cm squared.
