<span><span>9 - 3 = 6, 15-9 = 6 the difference is 6, So d = 6
</span><span>
First term: a1 = 3
Sn = n*(a1 + an)/2
Sn = n*(a1 + a1 + (n-1)*d)/2
Sn = n*(2*a1 + (n-1)*d)/2
</span></span>
<span> <span>substitute 26 for n
</span>
S26 = 26*(2*a1 + (26-1)*d)/2 </span>
<span><span>substitute 3 for a1
</span><span>
S26 = 26*(2*3 + (26-1)*d)/2 </span></span>
<span><span>substitute 6 for d
</span><span>
S26 = 26*(2*3 + (26-1)*6)/2 </span><span>
</span><span>
S26 = 2,028</span></span><span><span>
</span><span>
</span></span>
The fluid ounce of vanilla is bigger.
