Answer:
The third particle should be at 0.0743 m from the origin on the negative x-axis.
Explanation:
Let's assume that the third charge is on the negative x-axis. So we have:

We know that the electric field is:

Where:
- k is the Coulomb constant
- q is the charge
- r is the distance from the charge to the point
So, we have:

Let's solve it for r(3).
Therefore, the third particle should be at 0.0743 m from the origin on the negative x-axis.
I hope it helps you!
Beaker would be most appropriate for measuring the approximate volume of a liquid.
Since there is no decimal point in the number given above, the counting for the number of the significant figures will start from the left. Then, the first zero from the left is insignificant. Therefore, in this number there are 6 significant figures.