Completing the line Problem Story on rank and array

Sample Questions A building line has some seats, in the first row there are 25 seats fruit. While on the next line there are 5 seats more fruit from the previous line. If in building row seats have 15, how the number of seats in the whole building?
Settlement Description of problem, we can conclude that the problems that we face is a problem aritmetika array, not the line and not the array geometry, this can be simpulkan of the sentence "While on the next line there are 5 seats more fruit from the previous line." So we use penyelesainnya using the formula in the formula-array geometry, the formula to find the tribe and the amount of n-n array tribe first.
The first thing we do is create a variable that is known. Namely: U1 = 25 Beda (b) = 5 The formula to find the tribe - is n Un = U1 + (n - 1) b And find the formula n is the first tribe Sn = ½ nx (U1 + Un)
So to find the number of seats that must be done is for the number of seats on the last line to the line-15 U15 = U1 + (15 - 1) 5 = 25 + (14) 5 = 25 + 70 = 95 Then, on to the line - there are 95 fruit 15 seats Number of seats in the building because the S15 seats only 15 rows So S15 = 15 ½ x (25 + 95) = ½ x 15 (120) 120 divided by 60 ½ so that the living = 15 x 60 = 900 So the number of seats in the 900 building is the seat
Categories: rank and progression,Problem Stories