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Calculating electric field strength

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Homework Statement



http://img219.imageshack.us/img219/3310/problemi.png [Broken]

Homework Equations



F = kq/r^2

The Attempt at a Solution



O ----- x ----O -----------O

Let the electric field of the first O be E1, second be E2, third be E3.
RED - .02m
BLUE - .016m
GREEN - .033m

E1 = (9 * 10^9) (7.6 * 10^-6) / (.02^2) = 1.70763 * 10^8
E2 = (9 * 10^9) (1.6 * 10^-6) / (.016^2) = 5.61722 * 10^7
E3 = (9 * 10^9) (2.8 * 10^-6) / (.033 + .016)^2 = 1.04811 * 10^7

E1 and E3 are going -> and E2 is going <-.
So I figured the magnitude of the electric field strength would be the absolute value of E1 + E3 - E2 which turned out to be 1.25072 * 10^8 N/C.

However the answer is apparently wrong and I'm not sure where I made a mistake =\.
Any help is appreciated.

Never mind I caught my mistake after re-reading what I typed out...turns out I used 7.6 for the first charge instead of 7.9 :(
 
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