KVPY SX SB Exam 2012 Question Paper

Question : 18 of 120

Marks: +1, -0

The number o f ordered pairs (m,n), where m ,n ∈ {1,2,3,...,50}, such that

6^m + 9^n

is a multiple of 5 is

Solution:

\table ,6^m+9^n;6^1=6,,9^1=9;6^2=6,,9^2=1;6^3=6,,9^3=9;6^4=6,,9^4=1

m can be any value and n will be odd number then sum is multiple of 5
50× 25 = 1250

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