A student taking a test consisting of 10 questions is told that each question after the first question is worth 2 marks more than the preceding questions. If third question of the test worth 5 marks , what is the maximum score that the student can obtain by attempting 8 questions. 

The answer is 96 marks. I want explanation.

Dear student

The maximum marks can be scored by obtaining full marks from 3rd to 10th questions.

Here, a = 5, d = 2, n = 8
[Marks to 3rd question = 5, 10th question is 8th term when first term is 3rd question]
So, S8=n22a+(n-1)d=822×5+8-12=410+14=96
So, maximum mark that the student can obtain is 96.
Regards

  • 2
yes
  • -2
The answer is not 96. Let me show you. given, a3= 5, d= 2, n= 8. a3 = a+2d .: 5 = a + 2*2 .: a = 5-4 = 1 S8= 8/2 [ 2*1 + (8-1)2] = 4 [ 2+ 14 ] = 64.
  • -2
What are you looking for?