Ordered Pairs

How many ordered pairs of integers ( m , n ) (m,n) satisfy the equation m 20 = 15 n \dfrac{m}{20}=\dfrac{15}{n} ?

Two Permutations of the same solution i.e ( m , n ) a n d ( n , m ) (m,n) and (n,m) are considered different.


The answer is 36.

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1 solution

Mehul Arora
Apr 30, 2015

Cross Multiplying, We get, m n = 300 mn=300 . Now, 300 = 2 2 3 5 2 300={2}^{2}*3*{5}^{2} .

Therefore, 300 Can be expressed as a product of 2 or more integers In ( 2 + 1 ) ( 2 ) ( 2 + 1 ) = 18 w a y s (2+1)(2)(2+1)=18 ways . This is Because 300 has 18 factors.

But, Because m , n m,n are Integers and -m*-n=mn, Therefore 36 ways are possible.

I did it exactly the same way. Nice solution!!!

samuel ayinde - 6 years, 1 month ago

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Thanks! @samuel ayinde

Mehul Arora - 6 years, 1 month ago

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