Math Help Sequences And Series
July 4th, 2010
Question: HELP! math word probs, sequences & series!!?
1. how many integers between 50 and 500 are divisible by 7?
2. find the sum of the powers of 5 between 5 and 9765625, inclusive.
3. find the sum of the positive 3-digit odd numbers.
(how do i set up #1? for #2, i used the geometric sum formula, and i found out the rate was 5, but the time i did out the formula it ‘overflowed’ in my calculator…did i do it wrong? and for #3, i set it up so that i found asub1, asub2, asub3 (101, 103, 105) and found “d” to make the rule, then i used the arithmetic sum formula…but the answer i got isn’t right).
any help would be great.
Answer: Q 1)
64
7 * 71 is closest to 500 yet less
7*7 is 49 which is less than 50 so 7 ints. don’t work
71-7=64
Q2) done by hand overflowed calculator
12203903905
5^1+5^2+5^3+5^4+5^5+5^6+5^7+5^8+5^9
+5^10
Q3)( I forgot 0 but now fixed)
247500
101 to 999 added = ((900/2)*(101+999))/2
Sequences & Series: Summation (Sigma) Notation
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