A batsman makes a score of 87 runs in the 17th inning and thus increases his average by 4. Find his average after 17th inning. Choose the correct choice
A) 36	B) 39	C) 23	D) 45	E) none of the above

Rationale: "let the average after 17 th inning = x . then , average after 16 th inning = ( x – 4 ) . ∴ 16 ( x – 4 ) + 87 = 17 x or x = ( 87 – 64 ) = 23 . answer c"
Answer: C