SOLUTION: A man deposited 2000 in a savings bank paying him a certain interest. At the end of the year, he withdraw 150. At the end of the second year, the amount due to him was 1947.50. Wha

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Question 353718: A man deposited 2000 in a savings bank paying him a certain interest. At the end of the year, he withdraw 150. At the end of the second year, the amount due to him was 1947.50. What was the rate of interest?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
If r was the simple interest rate, he was due
2000+%2B+2000r at the end of the 1st year
Then he withdrew 150, so he had
2000%2A%281+%2B+r%29+-+150
At the end of the 2nd year, he was due
2000%2A%281+%2B+r%29+-+150+%2B+%282000%281+%2B+r%29+-+150%29%2Ar+=+1947.5
2000%2A%281+%2B+r%29+-+150+%2B+2000%28r+%2B+r%5E2%29+-+150r+=+1947.5
2000+%2B+2000r+-+150+%2B+2000r+%2B+2000r%5E2+-+150r+=+1947.5
2000r%5E2+%2B+1700r+=+1947.5+-+1850
2000r%5E2+%2B+1700r+=+97.5
2000r%5E2+%2B+1700r+-+97.5+=+0
solve using quadratic formula
r+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a+=+2000
b+=+1700
c+=+-97.5