# How much had Tarun scored in Math?

90 views

Tarun came second in Math. When his mother asked him how much he had scored, he answered that he got the sum of the first 9 even numbers. His mother immediately worked out the answer.
How much had he scored in Math?

posted Aug 6, 2015

72 or 90 depending
on whenever zero or
two comes first.

answer Aug 7, 2015 by anonymous
+1 vote

An even number is represented by '2n' in Algebra. The first nine even numbers are represented as follows
2n =1, where n=1
2*2n = 4,
4*2n = 6. Continuing in this way the sum of first nine even numbers will be,
2n+2*2n+4*2n+6*2n _ ...9*2n = 2n[1+2+3+4+5...9] = 2n X n (n+1) = 2n*9x10/2 = 2n * 45. Assume the value of 'n' to be 1. Substituting this value we get, 45*2 = 90. So Tarun's marks in Mathematics is 90. M J SUBRAMANYAM, BENGALURU.

answer Aug 8, 2015 by anonymous

Similar Puzzles

In a class test Tanay scored 160 marks in Geography and History together. If one third of his marks in Geography equals to half of the marks he scored in History, then how much has he scored in History?