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  1. Find 3^100(mod 100). this is 'a'
  2. Integrate f(3x-1) over 1 to 3. You should get a constant. Let this be 'b'.
  3. Now let there be a function g(x) which is ax^2+bx.
  4. What is g(ab)?
  5. Try not to use wolfram alpha.


The answer is 200.

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2 solutions

Avi Aryan
Jun 15, 2014

The real challenge in this question is finding 3 100 m o d 100 3^{100} mod 100 .
First of all, we must note that 'mod 100' of any number N N means the last 2 digits of N N .
Now 3 10 = 3 5 3 5 = 243 243 3^{10} = 3^5 * 3^5 = 243 * 243
The last 2 digits of 3 10 3^{10} can be found from 43 43 = 1849 = 49 43 * 43 = 1849 = 49 . So 3 10 3^{10} maybe a b c . . 49 abc..49 .


Similarly last 2 digits of 3 20 3^{20} = 3 10 3 10 = 49 49 = 2401 = 01 3^{10} * 3^{10} = 49 * 49 = 2401 = 01
Last 2 digits of 3 40 3^{40} = 01 01 = 01 01*01 = 01
Last 2 digits of 3 60 3^{60} = 3 40 3 20 = 01 01 = 01 3^{40} * 3^{20} = 01*01 = 01
...
Last 2 digits of 3 100 = 01 = 3^{100} = 01 = a

Aloysius Ng
Jun 2, 2014
  1. 'a' is 01

  2. 'b' is 10

  3. g(x) is x 2 + 10 x x^2+10x

  4. g ( 10 1 ) = g ( 10 ) = 1 0 2 + 10 10 = 200 g(10*1)=g(10)=10^2+10*10=**200**

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