86 *2 = 172
172/3 = 57.33
54 + 56 +58 =168
168/2 =84
56 + 58 +60 = 174
174/2 =87
58 +60 +62 = 180
180/2 = 90
60 +62 +64 = 186
186/2 = 93
62 +64+66 = 192
192/2 = 96
there are 3 sets of numbers that fall between 84 & 96
1 set equals 84 and 1 set equals 96
so if you are counting those there are 5 sets
First term: a1 = 151
common difference: d = -14 (we decrease by 14 each time, eg, 151-14 = 137)
nth term of this arithmetic sequence is...
an = a1+d(n-1)
an = 151+(-14)(n-1)
an = 151-14n+14
an = -14n+165
This will be used in the formula below
Sn = n*(a1+an)/2
<span>Sn = n*(151+(-14n+165))/2
</span><span>S26 = 26*(151+(-14*26+165))/2 ... replace every n with 26
</span>S26 = -624
The final answer here is choice C) -624
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Answer:
Step-by-step explanation:
- Height of cone (h) = 7 cm
- Formula for Volume of cone is given as:
- Plugging the values of h and r in the above formula, we find:
Simple. Just add/subtract each term. 4n-2n=2n. 8m+7m=15m.
This is very basic stuff.
