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## Homework Statement

A + 7.3 nC point charge and a - 2.4 nC point charge are 3.5 cm apart. What is the electric field strength at the midpoint between the two charges?

## Homework Equations

E = 9*10^9(q/r^2)

q = charge

r = distance from point charge

## The Attempt at a Solution

Since the question asks for the field strength between the two charges, r would be 1.75 cm or .0175 m.

Therefore

E = E1+E2

E1=9*10^9(7.3*10^-9/.0175^2)

E1=214531

E2=9*10^9(-2.4*10^-9/.0175^2)

E2=-70530.6

E=144000 N/C

Except it says I'm wrong. Its multiple choice, and the other choices given are

1900 N/C

5700 N/C

2.8×10^5 N/C