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# Simple yet complicated!? watch

1. Hi guys, this looks rather a simple problem but my calculator is not giving me the right answer. I am hoping someone here can guide me through..

I have the solution but how did they get this???

xv(1-v^240)/(1-v)

Let v = 1/(1.005)

I need to get the answer x = 716.43

I've spend many hours figuring out using my calculator but no luck. Any help on this 30 second question is appreciated!
2. That's an expression, not an equation - it can't be solved. Is there more to the question?
3. (Original post by PythianLegume)
That's an expression, not an equation - it can't be solved. Is there more to the question?
^^^ this ^^^
4. (Original post by fourdigit)

I need to get the answer x = 716.43
You need to tell us the question
5. (Original post by PythianLegume)
That's an expression, not an equation - it can't be solved. Is there more to the question?
Thanks for your quick response and feedback PythianLegume.

There is more to the questions but I believe I provided the relevant values and expression needed to get the value of x. Because the rest of the workings were simplified to get to this final line.
6. (Original post by TenOfThem)
You need to tell us the question
Thanks TenofThem. I'll try
7. (Original post by fourdigit)
Thanks for your quick response and feedback PythianLegume.

There is more to the questions but I believe I provided the relevant values and expression needed to get the value of x. Because the rest of the workings were simplified to get to this final line.
Based on the numbers you've provided, I assume that the expression is supposed to equal 10,000?
8. (Original post by PythianLegume)
That's an expression, not an equation - it can't be solved. Is there more to the question?

(Original post by TenOfThem)
^^^ this ^^^

A 20 years loan of 100,000USD has been granted. Rate of interest is 6% p.a. The person is repaying his loans in monthly instalments. Calculate the initial monthly instalment.
9. (Original post by PythianLegume)
Based on the numbers you've provided, I assume that the expression is supposed to equal 10,000?
100,000 Yes! Any luck?
10. (Original post by fourdigit)
100,000 Yes! Any luck?
Yes, 100,000 sorry. If you just take the expression in your OP and say it's equal to 100,000, then you can solve to find x.

xv(1-v^240)/(1-v) = 100,000.

Simply substitute 1/1.005 for v, rearrange the equation to make x the subject, and solve.

However, I can't see where the expression comes from based on the loan example you gave.
11. (Original post by PythianLegume)
Yes, 100,000 sorry. If you just take the expression in your OP and say it's equal to 100,000, then you can solve to find x.

xv(1-v^240)/(1-v) = 100,000.

Simply substitute 1/1.005 for v, rearrange the equation to make x the subject, and solve.

However, I can't see where the expression comes from based on the loan example you gave.
Thanks PythianLegume, I believe my understanding on rearranging fractions to make the subject x seems to be the problem. Can you kindly able yo highlight my problem.

By making the value x the subject, and taking into account that the example is an fraction, I cross-multiplied both side. Then I crossed out (1-v) from both sides, and subtracted 100,000 by v(1-v^240). Giving me x = 100,000 - v(1-v^240)

Of course, I don't get the right answer so I must be doing something wrong in rearranging the formula.
12. (Original post by fourdigit)
Thanks PythianLegume, I believe my understanding on rearranging fractions to make the subject x seems to be the problem. Can you kindly able yo highlight my problem.

By making the value x the subject, and taking into account that the example is an fraction, I cross-multiplied both side. Then I crossed out (1-v) from both sides, and subtracted 100,000 by v(1-v^240). Giving me x = 100,000 - v(1-v^240)

Of course, I don't get the right answer so I must be doing something wrong in rearranging the formula.
xv(1-v^240)/(1-v) = 100,000

Multiply by (1-v), xv(1-v^240) = 100,000 - 100,000v
Divide by v x(1-v^240) = 100,000/v - 100,000 = 100,000(1/v - 1)
Divide by (1-v^240), x = 100,000(1/v - 1)/(1-v^240)

I'm not sure if you can simplify this last part, but you'll be using a calculator, so don't need to.
13. (Original post by PythianLegume)
xv(1-v^240)/(1-v) = 100,000

Multiply by (1-v), xv(1-v^240) = 100,000 - 100,000v
Divide by v x(1-v^240) = 100,000/v - 100,000 = 100,000(1/v - 1)
Divide by (1-v^240), x = 100,000(1/v - 1)/(1-v^240)

I'm not sure if you can simplify this last part, but you'll be using a calculator, so don't need to.
Thanks PythianLegume, I was able to understand your calculations. Just when I substitute the values into my calculators, the closest figure even with all the digits, I get x = 712.87 and not 716.43.

I'll have a look at my calculations later, too much exercises. But thanks for your consistent help! Thank you!
14. (Original post by PythianLegume)
xv(1-v^240)/(1-v) = 100,000

Multiply by (1-v), xv(1-v^240) = 100,000 - 100,000v
Divide by v x(1-v^240) = 100,000/v - 100,000 = 100,000(1/v - 1)
Divide by (1-v^240), x = 100,000(1/v - 1)/(1-v^240)

I'm not sure if you can simplify this last part, but you'll be using a calculator, so don't need to.

Thanks, I managed to solve the calculation, the last line needed to be amended

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