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A math prob, pls help

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tracyyahoo Master | Next Rank: 500 Posts Default Avatar
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A math prob, pls help

Post Mon Oct 03, 2011 10:15 pm
Alex deposited x dollars into a new account that earned 8 percent annual interest, compounded annually. One year later Alex deposited an additional x dollars into the account. If there were no other transactions and if the account contained w dollars at the end of two years, which of the following expresses x in terms of w ?

a: w/1+1.08
b: w/1.08+1.16
c: w/1.16+1.24
d: w/1.08+1.08^2
e: w/1.08^2+1.08^2


my approach is :
deposit is x:
(1.08){x(1+0.08)}=w, then x=w/1.16*1.08

Am I missing anything here?? Pls explain....


No, No, I calculate in a wrong way, I chose B~~!!!! Pls explain in details and give me a full calculation process!!! Thank you



Last edited by tracyyahoo on Mon Oct 03, 2011 10:34 pm; edited 2 times in total

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shankar.ashwin Legendary Member Default Avatar
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Post Mon Oct 03, 2011 10:27 pm
At the end of 2 years you have

w = 1.08(1.08x) + 1.08x

1.08(1.08x) - 8% interest on amount after first year
1.08x - Interest on 'x' deposited the second year.

so,

x = w/1.08+1.08^2 D


PS: your equation (1.08){x(1+0.08)}=w

It shoud be (1+1.08) and not (1 + 0.08)

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sl750 Master | Next Rank: 500 Posts
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Post Mon Oct 03, 2011 10:24 pm
Nothing wrong with your answer. You should just rearrange it

Answer d can be written as w/1.08(1+1.08) = w/1.08*2.08

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