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Find the sum of all multiple 3 between 5 and 64

User RonSiven
by
8.0k points

2 Answers

3 votes

Answer: ∑=690

Explanation:

Let's use the formulas for an arithmetic progression:


a_1=6 \ \ \ \ \ a_n=63\ \ \ \ d=3\\a_n=a_1+(n-1)d\\63=6+(n-1)3\\63=6+3n-3\\63=3+3n\\63-3=3+3n-3\\60=3n\\

Divide both parts of the equation by 3:


20=n

Thus,


\displaystyle\\\sum=(a_1+a_n)/(2) n\\\\\sum=(6+63)/(2)20 \\\\\sum=(69*20)/(2) \\\\\sum=69*10\\\\\sum=690

User Alexey Mukas
by
7.6k points
4 votes

Answer:

690

Explanation:

The multiples of 3 between 5 and 64 are 6+9+12+15+18+21+24+27+30+33+36+39+42+45+48+51+54+57+60+63 which gives you 690.

Hope this helps, have a good day! :D

User DSoldo
by
7.8k points

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