Question

In cinema hall there are 1656 seats and
in the last row are 105 seats in each next
row 3 seats less. How many are the total Rou.
in cinema Hall?
& sn=1656
105, !02,99,-
(And t 23who will answer this question correctly I will mark them as brain list​

Answer 1

Answer:

23 and 48

Step-by-step explanation:

105 , 102 , 99 ........

This is an A.P. whose sum = 1656

a = 105

d = -3

Sum = 1656

n = ??

Sum = n [2a + (n-1) d]

           2

1656 = n [2* 105 + (n-1) (-3)]

             2

1656 * 2 = n [210 -3n + 3]

3312 = n [213 - 3n]

3312 = 213n - 3n²

3n² - 213n + 3312 = 0

n = 23 and 48

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