Answer :
let the series be a , a+d, a+2d , .....
sum of the first 9 terms: [2 a + 8 d] * 9/2 = 9 a + 36 d
so 200 <= 9 a + 36 d <= 220
2nd term : a + d = 12 => 9a = 9 (12 - d) = 108 - 9 d
=> 200 <= 108 - 9d + 36 d <= 220
=> 92 <= 25 d <= 112
=> 3.6 <= d <= 4.4
=> d = 4 as d is a natural number and a is also a natural number.
=> a = 12 - 4 = 8.
series: 8, 12, 16, 20, 24, ... sum of the first 9 numbers: 216
sum of the first 9 terms: [2 a + 8 d] * 9/2 = 9 a + 36 d
so 200 <= 9 a + 36 d <= 220
2nd term : a + d = 12 => 9a = 9 (12 - d) = 108 - 9 d
=> 200 <= 108 - 9d + 36 d <= 220
=> 92 <= 25 d <= 112
=> 3.6 <= d <= 4.4
=> d = 4 as d is a natural number and a is also a natural number.
=> a = 12 - 4 = 8.
series: 8, 12, 16, 20, 24, ... sum of the first 9 numbers: 216
Answer:
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