Answers

2016-07-17T05:54:59+08:00
 a_{1} = 16  a_{n}  = 48

n = 9 [ There are 9 multiples of 4 between 15 and 49 ]

Then apply this formula..

 S_{n} = n/2 [  a_{1}  +  a_{n}  ]

Substitute the given above

 S_{n} = 9/2 [ 16 + 48  ]

= 9/2 ( 64 ) [ Cancel 2 and 64 ]

= 9 ( 32 ) [ Simplify ]

 S_{n} = 288  [  Note:  S_{n} = sum of terms ]
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