Rows of chairs

There are 15 chairs in the first row. There are 3 more chairs in each row. How many chairs are there in the first 20 rows?

Correct answer:

s =  870

Step-by-step explanation:

a1=15 d=3 n=20  a20=a1+(201) d=15+(201) 3=72  s=2a20+a1 n=272+15 20=870



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You need to know the following knowledge to solve this word math problem:

algebraarithmeticplanimetricsbasic functionsGrade of the word problem

 
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