Word problem find equations then solve

  • Thread starter Thread starter synergix
  • Start date Start date
  • Tags Tags
    Word problem
Click For Summary

Homework Help Overview

The problem involves calculating the principal amount and interest rate based on a simple interest scenario. The original poster presents a situation where a certain amount of money yields $19.36 in interest over one year, with variations in principal and interest rate leading to the same interest outcome.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to derive two equations from the problem statement but encounters complexity in their solution. Some participants suggest re-evaluating the manipulation of the equations, while others encourage sharing calculations to identify potential errors.

Discussion Status

The discussion includes attempts to solve the equations, with one participant noting a mistake in their calculations that led to an incorrect answer. There is an indication that further clarification and assistance may be provided as participants engage with the original poster's work.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may impose specific methods or formats for presenting solutions. The original poster's equations are derived from the problem's conditions, but there is uncertainty regarding their manipulation and resulting calculations.

synergix
Messages
177
Reaction score
0

Homework Statement



A certain amount of money saved for 1 year at a certain annual interest rate(simple interest) yielded 19.36$ in interest. if we had added $66 to the principal and reduced the interest rate by 3 percentage point(s), the interest would have been the same, Find the principal and the rate.


Homework Equations



(1)$19.36= PR
(2)$19.36=(P+$66)(R-0.03)


The Attempt at a Solution



I solved (1) for P then substituted that into equation (2)and I got a complex answer so I must have incorrectly formed the equations any help?
 
Physics news on Phys.org
If I solve those equations I get a real answer which seems reasonable too. You must have incorrectly manipulated them.
Can you try typing out your calculation? If you don't spot the error while typing it, we might be able to help you find it.
 
Ok here you go.

first I solved (1) for R
R=19.36/P
Then I put that into (2)
19.36=(P+66)((19.36/P)-0.03)
(19.36=19.36-0.03P+1277.76/P-1.98)P
19.36P-19.36P=-0.03P-1.98P+1277.76
Then I divided by -0.03

0=P^2+66P-42529

and I found my mistake... when I used the quadratic formula and multiplied -4ac I kept it negative and therefore ended up with a large negative square root and an imaginary answer D'oh
THX!
 
P=176 r=0.11
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
Replies
1
Views
1K
Replies
11
Views
2K
  • · Replies 12 ·
Replies
12
Views
8K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
2K