I have raised $4978 for charity.
How many benefactors are there?
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Let x be the number of men and y the number of women. We can set up a diophantine equation: 6 7 x + 5 9 y = 4 9 7 8
By Euclidean algorithm, we can calculate:
6 7 = 5 9 + 8
5 9 = 8 • 7 + 3
8 = 3 • 2 + 2
3 = 2 • 1 + 1
Then 1 = ( 5 9 − 8 • 7 ) − ( 8 − 3 • 2 ) = 5 9 • 2 5 − 2 2 • 6 7
Thus, 4 9 7 8 = 5 9 ( 2 5 • 4 9 7 8 ) − 6 7 ( 2 2 • 4 9 7 8 ) .
That is, x 0 = − 2 2 • 4 9 7 8 and y 0 = 2 5 • 4 9 7 8 .
Since 6 7 and 5 9 are coprime, x = x 0 + 5 9 n > 0 and y = y 0 − 6 7 n > 0 .
Hence, 6 7 2 5 • 4 9 7 8 > n > 5 9 2 2 • 4 9 7 8 .
Only n = 1 8 5 7 works.
As a result, x = − 2 2 • 4 9 7 8 + 5 9 • 1 8 5 7 = 4 7 .
y = 2 5 • 4 9 7 8 − 6 7 • 1 8 5 7 = 3 1 .
Finally, the total benefactors= 4 7 + 3 1 = 7 8 .