Question 1088070
Students created a trapezoid from the cans they had collected
for the food bank. There were 10 rows in the trapezoid. The 
bottom row had 100 cans. The 10th row has 136 cans. How many 
cans were in the 8th row?
<pre>
It's an arithmetic sequence

{{{a[n]=a[1]+(n-1)d}}}
</pre>
Students created a trapezoid from the cans they had collected 
for the food bank. There were 10 rows in the trapezoid. 
<pre>
{{{n=10}}}
</pre>
The bottom row had 100 cans. 
<pre>
{{{a[1]=100}}}
</pre>
The 10th row has 136 cans. 
<pre>
{{{a[10]=135}}}

Substitute n=10 in

{{{a[n]=a[1]+(n-1)d}}}

{{{a[10]=a[1]+(10-1)d}}}

Substitute for {{{a[10]}}} and {{{a[1]}}}
and simplify:

{{{136=100+(9)d}}}

{{{36=9d}}}

{{{4=d}}}

So each row had 4 more cans than the preceding row.
</pre>
How many cans were in the 8th row?
<pre>
Substitute a<sub>1</sub> = 100, n=8, and d=4 in

{{{a[n]=a[1]+(n-1)d}}}

You finish.

Edwin</pre>