Question 758953
Let n = the number of people who had promised to contribute
Let c = the pledged contribution amount
Since the required amount was $600, we have
n*c = 600
The new number of contributors = n - 5, and their contribution amount = c + 10
The amount raised is still the same, so we can write
(n-5)(c+10) = 600
Solve for c in the 1st equation, substitute in the 2nd:
(n-5)(600/n+10) = 600
Multiply and collect terms:
600 + 10n - 3000/n - 50 = 600
10n - 3000/n - 50 = 0
Multiply through by n, divide by 10:
n^2 - 5n - 300 = 0
Factor:
(n+15)(n-20) = 0
This gives n=20 (positive solution)
So the actual number of subscribers is 20-5 = 15
Their contribution was $40
Check:
15*40 = (15+5)(40-10) = 20*30 = 600