"1. Let b1, b2, ...., b19 be the first 19 terms of anarithmetic progre

1.	"1. Let b1, b2, ...., b19 be the first 19 terms of anarithmetic progression (AP) with b1+ b8 + b 12 +b19 = 224. The sum of first 19 terms of the AP is(1) 448(2) 896(3) 1064(4) 1344
Answer» b1, b2, b3, _ _ _, b19 are in A.P b1 + b8 + b12 + b19 = 224 b1 = a b8 = a + 7d b12 = a + 11d b19 = a + 18d a + (a + 7d) + (a + 11d) + ( a + 18d) = 224 4a + 36D = 224 a + 9d = 56 a = 56 - 9d sum of first 19 term Sn = N/2 [ 2a + (n - 1) d ] = 19/2 [ 2 ( 56 - 9d ) + (19 - 1) d ] = 19/2 [ 112 - 18d + 18d ] = 19 × 56 = 1064 OPTION 3 is correct

"1. Let b1, b2, ...., b19 be the first 19 terms of anarithmetic progression (AP) with b1+ b8 + b 12 +b19 = 224. The sum of first 19 terms of the AP is(1) 448(2) 896(3) 1064(4) 1344

Answer»

b1, b2, b3, _ _ _, b19

are in A.P

b1 + b8 + b12 + b19 = 224

b1 = a

b8 = a + 7d

b12 = a + 11d

b19 = a + 18d

a + (a + 7d) + (a + 11d) + ( a + 18d) = 224

4a + 36D = 224

a + 9d = 56

a = 56 - 9d

sum of first 19 term

Sn = N/2 [ 2a + (n - 1) d ]

= 19/2 [ 2 ( 56 - 9d ) + (19 - 1) d ]

= 19/2 [ 112 - 18d + 18d ]

= 19 × 56

= 1064

OPTION 3 is correct

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"1. Let b1, b2, ...., b19 be the first 19 terms of anarithmetic progression (AP) with b1+ b8 + b 12 +b19 = 224. The sum of first 19 terms of the AP is(1) 448(2) 896(3) 1064(4) 1344​

OPTION 3 is correct

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"1. Let b1, b2, ...., b19 be the first 19 terms of anarithmetic progression (AP) with b1+ b8 + b 12 +b19 = 224. The sum of first 19 terms of the AP is(1) 448(2) 896(3) 1064(4) 1344