The sum of an Arithmetic Series is given as:

where,
d = Common Difference = Difference of any two consecutive terms.
So,
d = 8
a1 = First term = 1
Using the values, we get:

The above equation gives the formula for n terms of an Arithmetic Series.
So, option A is the correct answer
Answer: 140°
Step-by-step explanation:
look at the little number
Answer:
No. The solution is 
Step-by-step explanation:

When we say two quantities
and
are proportional to one another, there are two ways we could mean this.
- If
is *directly* proportional to
, then we mean that as
changes,
changes in the same direction. In other words, if
is in/decreased, then
also in/decreases. The rate of in/decrease doesn't have to be one-to-one; for example, we could have
increase by 1 unit while
would proportionally increase by 5 units. In this case, we'd have
.
- On the other hand, if
is *inversely* proportional to
, then a change in
results in a change in
that goes in the opposite direction. A common example involves taking a rectangle of constant area and adjusting the width
and length
. If the rectangle has an area of 5 square units, then we could have
and
, or we could have
and
, or
and
, or any combination of
and
such that
is satisfied.
In both cases, we call 5 the "constant of proportionality".
On to your exercises:
(1a) Looks like
stands for number of apples. Then we're told that the cost
, which means that for every apple, the cost increases by 2.3 dollars. So the constant of proportionality is 2.3. In the language of proportionality, we could then say that the cost of apples is directly proportional to the number of apples by a factor of 2.3.
(1b) 5.4
(1c) 12.5
Answer:

And we can subtract 4x in both sides and we got:

Now we can subtract in both sides 16 and we got:

And if we divide both sides by 4 we got:

And the best solution would be:
-7
Step-by-step explanation:
For this case we assume the following equation:

And we can subtract 4x in both sides and we got:

Now we can subtract in both sides 16 and we got:

And if we divide both sides by 4 we got:

And the best solution would be:
-7