Calculate Value Resistance Which Must Connected Resistance Provide Effective Resistance

Calculate the value of the resistance which must be connected to a 15 ohm resistance to provide on effective resistance of 6 ohm.

Answers:

Resistance decreases in parallel combination. S let R resistance is connected to 15 Ω resistance parallel to make resultant 6 ohm.

Now, 1/6 = 1/15 + 1/R

Or  1/R = 1/6 – 1/15

= 5 – 2/30 = 3/30 = 1/10

∴ R = 10Ω