Calculation of Total Resistance:

When resistors are connected in parallel, the total resistance can be calculated using the formula:

1/Rt = 1/R1 + 1/R2 + 1/R3 + ...

In this case, there are three resistors connected in parallel: 2 ohm, 4 ohm, and 5 ohm. Therefore, the total resistance can be calculated as follows:

1/Rt = 1/2 + 1/4 + 1/5

To simplify the calculation, we can find the common denominator by multiplying 2, 4, and 5:

1/Rt = 10/20 + 5/20 + 4/20

1/Rt = 19/20

Taking the reciprocal of both sides, we get:

Rt = 20/19 ≈ 1.05 ohm

Therefore, the total resistance of the combination is approximately 1.05 ohm.

Calculation of Current through each Resistor:

To calculate the current through each resistor, we can use Ohm's Law, which states that the current (I) flowing through a resistor is equal to the voltage (V) across the resistor divided by its resistance (R):

I = V/R

Given that the battery has an EMF of 20 volts and negligible internal resistance, the voltage across each resistor will be the same.

Using the formula, we can calculate the current through each resistor:

For the 2 ohm resistor:
I1 = 20/2
I1 = 10 amperes

For the 4 ohm resistor:
I2 = 20/4
I2 = 5 amperes

For the 5 ohm resistor:
I3 = 20/5
I3 = 4 amperes

Therefore, the current flowing through the 2 ohm resistor is 10 amperes, the current flowing through the 4 ohm resistor is 5 amperes, and the current flowing through the 5 ohm resistor is 4 amperes.

Calculation of Total Current Drawn from the Battery:

The total current drawn from the battery is the sum of the individual currents through each resistor. Therefore, the total current can be calculated as follows:

Itotal = I1 + I2 + I3

Substituting the values we calculated earlier:

Itotal = 10 + 5 + 4
Itotal = 19 amperes

Therefore, the total current drawn from the battery is 19 amperes.

In summary, the total resistance of the combination of the three resistors connected in parallel is approximately 1.05 ohm. The current flowing through the 2 ohm resistor is 10 amperes, through the 4 ohm resistor is 5 amperes, and through the 5 ohm resistor is 4 amperes. The total current drawn from the battery is 19 amperes.