find the sum of last 15 terms of an Ap with a=5, d=7 and it has 50 terms
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Answered by
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a = 5
d = 7
n = 50
L = a +(n-1) d
L = 5 + (50 - 1)7
L = 5 +49× 7
L = 5 + 343
L = 348
Now,
Arrange the given AP in descending order.
348, 341, 334.....
a = 348
d = - 7
n = 50
S50 = 15/2[ 2 × 348 + (15-1)(-7)]
= 15/2 [ 696 + 14(-7)]
= 15/2 [ 696 - 98 ]
= 15 × 598 / 2
= 15 × 299
= 4485
d = 7
n = 50
L = a +(n-1) d
L = 5 + (50 - 1)7
L = 5 +49× 7
L = 5 + 343
L = 348
Now,
Arrange the given AP in descending order.
348, 341, 334.....
a = 348
d = - 7
n = 50
S50 = 15/2[ 2 × 348 + (15-1)(-7)]
= 15/2 [ 696 + 14(-7)]
= 15/2 [ 696 - 98 ]
= 15 × 598 / 2
= 15 × 299
= 4485
trisha37:
wrong
Answered by
17
a = 5
d = 7
n = 50
L = a +(n-1) d
L = 5 + (50 - 1)7
L = 5 +49× 7
L = 5 + 343
L = 348
Now,
Arrange the given AP in descending order.
348, 341, 334.....
a = 348
d = - 7
n = 50
S50 = 15/2[ 2 × 348 + (15-1)(-7)]
= 15/2 [ 696 + 14(-7)]
= 15/2 [ 696 - 98 ]
= 15 × 598 / 2
= 15 × 299
= 4485
hope it helped ❤️
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